post and boot problems after removing USB device

Hi all,

Just last week I rebuilt my PC (I believe my old processor died). Brand new motherboard, processor, and RAM. Other hardware is relatively new (less than a year). Specs are below. After wrestling to get winXP (SP3, but updated from SP1) running again (moving on to linux after this!), everything seemed to be running smoothly. This afternoon, I was rearranging some telephone cable, and unplugged a MagicJack device (I know, they're junk) from a USB port while the machine was running, and suddenly my machine starting booting and rebooting on its own (without ever loading windows). After pulling power, I was able to reboot and get into BIOS settings, and removed "USB YMAX" (the MagicJack) from the boot sequence (apparently it put itself there in position 4); still wasn't able to load windows (I think it was rebooting itself again at this point); at some point I restored all the default settings. Now I can't seem to post at all. Sometimes I'll get as far as a memory check, then I just freeze. Sometimes I get nothing but a blank screen. Can't boot from a CD either. I also tried unplugging all the USB devices; no change.

Things I have NOT tried yet are: clearing CMOS, re-seating hardware.

Could I have somehow caused a short? Or is this more likely a software issue?

Any thoughts anyone might have would be greatly appreciated. I'm a pseudo-newbie in this department, but I learn fast! Cheers.

Specs:

mobo: ASRock 4CoreDual-SATA2 LGA 775 (Via PT8880 Pro/PT880)
CPU: Intel Core 2 Duo E7200 Wolfdale
mem: Kingston DDR2 667 (2 x 1GB)
video: Sapphire RADEON 9600 (AGP 8x)
PSU: Enermax Noisetaker II (420W)
HD: WD SATA1 80gb