My 65W adapter gets incredibly hot during charging, and I think it may have something to do with my machine thinking it's a 90W adapter. In the Power Manager application, on the Battery tab, it says "90W AC adapter is attached." Is there some way to fix this? Or do I need to replace the adapter?

good question..
if you have another adapter available, try it and see what the thinkpad reports..
if it reports the correct adapter, then replace the other adapter as defective..
if it reports the wrong adapter then IMO the thinkpad needs to have warranty service done on it..

be sure to reboot to see if this might be a software issue..

The signal (on centre pin) is broken, inside the plug, impossible to detect by eye. Sixty-five watt supply has a resistor inside, ninety has not. So, without signal, any adapter is sensed as ninety watt.

Further reading if you are curious:
viewtopic.php?p=682644#p682644

very good work mr. err. . .pada..
now i learn something..

Thanks for the info. I can't believe someone actually went and figured all of this out