Today I'm stuck doing a very long (ie 20 hrs) data-recovery scan of a 2TB external drive that I discovered today had a blown-up partition table.

The first run, after 3-4 hours I needed to move the drive slightly and after moving it gently and literally an inch (with plenty of cable slack) it momentarily disconnected from the system. Groan, all that effort lost, I'll start it again later.

That was in a Vantec USB 3.0/eSATA 3.5" enclosure that's been generally reliable in the past.

The 2nd time around I decided to move the drive to another enclosure that had also worked fine for me in the past (a Kingwin, USB 3.0 only), and I switched my previous USB controller (flush-mounted dual USB 3.0 ExpressCard) with a more 'traditional' express card with the protruding dongle (A Siig product), thinking the jacks might be more stable than the 'inside hide' ones.

This time, after something like 8 hours, I had no choice but to move it slightly again. (space is at a premium around here at the moment)

BOOM, disconnected again. ARGGGGH!

Is this an achilles-heel with these 'full size" USB 3.0/Superspeed USB cables? I don't recall ever having this kind of problem with USB 2.0 cables in the past.

Ouch! I'd hate that. Sorry I dont have much experience with USB 3 cables to comment. I am curious which S/W Tools/ Utils are you using to Scan/ Recover it? I want to make sure I am not missing something from my arsenal of tools
I had once hand recovered several partitions using PTEDIT (from PQMagic).

Yep, I think by "PQMagic" you're probably thinking of Powerquest, which was bought by Symantec. They made some groundbreaking tools, first company ever to develop a way to do a disk image without shutting down Windows I believe. Shame that Symantec killed-off Partition Magic, that was also a groundbreaking product. Symantec had a habit of buying their competitors and then killing their competing products. (Most of the old Powerquest tools are useless on modern SATA/64-bit-based systems and large disks, but apparently some of the original Powerquest people did eventually found a new company called StorageCraft. I evaluated their server backup product a while back which seemed promising but I didn't pursue it further after I concluded it was missing a couple of features I needed.)

I have been trying a few different things. The issue I have is the NTFS partition showed up as "RAW" in Windows, which apparently usually means some sort of partition table issue.

I thought that it was just a matter of fixing-up the partition table, but my first attempt to do that (using an open-source tool called TestDisk) didn't work. (and you never know whether what you just did made matters worse by removing clues that some other tool might have used to get it back to the way it was previously configured)

Then there are these 'free' utilities that claim to recover either the partition or files from it, but I had gotten confused by one company's offerings (Easeus - they have a slew of slightly different 'free' utilities) and started using one more focused on 'file recovery' - which was the original tool one that wanted to scan the disk for ~20 hours. But after the false starts/crashes noted above and many hours of scanning, I discovered that it only had this hard-coded list of 'known file types' that it would look for, and some of the most important files I needed that were on there (backups made via Acronis image backup software) weren't in their stupid list.

So I'm trying a 'demo' product right now from DiskInternals, but once again this one wants to take the better part of a day to scan the disk and then since it's a 'demo' I have no idea what happens then. Sorry to say I'm afraid it's going to tell me "Good news, after that ridiculously-long scan we now know we can recover this disk, you just have to buy the full product and start the process all over again!"

I thought that the thing I'm running now would just tell me quickly if it could fix-up the partition table or not so I could decide whether to throw money at them, but I was wrong. More waiting...

I was trying to avoid the 'scan forever' or "boot from archaic DOS disk on old computer" type of stuff at least initially, I already have licenses to some traditional data recovery tools. (ie Media Tools Professional, GetDataBack for NTFS) But because this disk is so big, most of these things seem to scan the disk for the better part of a day before you get off first base.

So I had moved this disk-scanning process on Saturday to a different Thinkpad (which happens to be running Windows 8 Consumer Preview) so it wouldn't tie-up my main laptop. After trying a different utility to scan the disk, I let it run for a few hours only to find that the LT had mysteriously and unexpectedly just powered-off. Event-log shows 'unexpected shutdown'. Several hours lost.

I thought it might have been some weird power profile so I checked/updated that, made sure there was no standby timeout, etc etc. Did I accidentally bump a cable or something?

So I started the process again, it had been running for something like 16 hours. I was working on the main LT and periodically watching the scan progress bar. I noticed it had finished and was displaying a modal dialog box. Finished what I was doing (maybe 1-2 minutes), went to move the trackpoint, found the LT had completely powered-off.

ARGGGGGGHHH!!

Whole weekend wasted on that, with zero progress.

Moral of story: don't use beta operating systems for anything important, even if they seem to be working fine...

Have you tried an eSATA cable and connect it to a (more stable) PC?

Well the last round described above was actually using an eSATA Cardbus card. I bought a new drive enclosure on Saturday that also supported both USB 3.0 and eSATA (somewhat hard to find) and this one also has a cooling fan on it because I noticed the old passively-cooled enclosures were getting awfully hot with this Barracuda XT drive inside running continuously for the better part of a day.

But it was the same Win8CP laptop, because my other 2 Thinkpads have XP on them and I would have to go through the whole process of finding and installing the right drivers on them (feel like USB 2 would be too slow and worried about USB cable flakiness again), and not sure (especially in eSATA mode) if I'll have issues with 4k sector compatibility. (though if I recall correctly this Seagate drive emulates 512b sectors)