i have the same prob before.. this is what i did..
while the psp is in "please wait...mode"
click "start" (from PC) go to programs..control panel.. administrative tools...computer management...system tools then device manager
you should see a "yellow question mark" with a "PSP" on it, double click it and let the wizard find for the best driver, if something pops up, click, "continue anyway" there you go.. hope this will solve your prob
When it say please wait, press circle, then go back into USB Mode. If that doesn't fix it; then try reseting the PSP.
Or try another USB cable, this problem has become very popular now and I wonder if everyone's USB cables are acting up now, or something is up with the PSP.