portable apps stopped opening

As a new portable apps user I am excited about the possibilities, but am probably my own worst enemy right now. Things had been working fine, then I started getting error messages when closing out and ejecting...it said some apps were still open but I'm sure everything was closed. That got more frequent, then it started locking up my XP system when I plugged it in...everything froze...had to hold my start button in to shut down, pull out, and reboot. Now the U3 icon that used to show up when I plugged in does not, and none of the U3 apps will open.
Which foot did I shoot ? Any suggestions please to get back to original start ?