I'm suddenly getting errors on one of my ext3 partitions during the boot
process, and Firefox has suddenly started acting like it's a brand new
installation each time I start it (the effected filesystem is where my
home directory is located, but not the main linux installation), and
Thunderbird did the same, although only once (Firefox is doing it all
the time). None of my other programs that I normally use are appearing
affected, although I haven't run through everything on my system yet.

The only thing I've done anywhere near recently that's abnormal is hook
up another hard drive to the system to copy files off of it, although
I'm not sure how this would affect the filesystem. My computer has not
had any sudden poweroffs in well over a year.

Aside from any sort of recent tampering that I've done, this partition
happens to be the oldest on the system - I created it to store all my
files in the case that I messed the OS up and needed to reinstall (thus
lessening the need of a backup before I tried some new program on my
system). I'm not sure if this has anything to to with it, but I'll
mention it anyways just in case.

Should I attempt to wipe my whole drive and reinstall, or is there some
other way of going about this to fix it?

I do plan to run fsck in a bit to see if that'll help any (although it
didn't on boot), after I've finished updating my backups.