When you say "forcing me to relaunch" do you mean that you get the spinning beach ball or that the screen turns grey and OS X tells you that you must reboot. If it is the latter, then it is probably a hardware-related issue (such as bad memory or a heat problem). Either way you could test software issues first:
1) Try running without loading any of your startup items (press the shift key BEFORE you submit your user ID and password during the login process and don't let go until you are up and running) and see if the machine locks when you access the drive.
2) Boot in safe mode (hold the shift key while you reboot) and see if the machine locks when you access the drive.
3) Backup up your entire hard drive to an external drive, then delete all of your preferences in ~/Library/Preferences and /Library/Preferences--perhaps starting with the preferences related to the applications that are known seem to be correlated with the problems. When you delete these files, you are normally reset to have the default settings. These files often get corrupted and cause problems. You can always copyt these files from the backup location after you finish your test.
5) Defrag your hard drive. Also, you drive should be less than half full. If it is 90% full, then you are asking for problems. You can search here or in other forums to get defrag tips.
6) If you can clone your entire drive to an external drive and then reformat your hard drive and test it without loading any special software, that might tell you if there is a problem with one of your extra applications that you added.
If it still crashes after doing all this, it is probably a hardware problem like bad memory, a heat problem, something loose inside and would need service.
See what other people say over the next couple days.