Vista Tutorial - usb 2.0 controller

anyone give me some info on usb 2.0 controller.i came home from
work and found my antivirus (avast) and flash drive not working .
rebooted the system and the antivirus came back on but the flash
drive didn't. when i pulled the drive out and put it in another
usb port the light comes on and then go's right out. so i rebooted
again and looked in the bios and found the usb 2.0 controller (disabled)
no one else uses this system . and it was working last night before i when
to work.i enabled it and the drive is back and working fine . but i'd like to no
what can cause something like that to happen.

vista home prem 64bit
GIGABYTE GA-EP45-DS3R (rev. 1.0)
Intel Core 2 Duo E8400 / 3.00 GHz processor ( clocked to 3.6 ghz )
SAPPHIRE 100225L Radeon HD 3870 512MB 256-bit GDDR4 PCI Express 2.0 x16
G.SKILL 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 1000 (PC2 8000) Dual Channel Kit
Crucial Ballistix 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 1066 (PC2 8500) Dual
NINJA PLUS Rev.B 6Heat Pipes CPU Cooler with fan
Thermaltake Toughpower 600W Power Supply
thanks scrooge

It could have been any of a numbe of things - but first and foremost I'd perform some online scans (including the USB drives).

Here are some links you may wish to use:

Online Scanners

TrendSecure | HouseCall™ Free Scan

BitDefender Online Scanner - Free Online Virus Scan (Internet Explorer only)

Free Virus Scan - Kaspersky Lab

Insalled AV scanners:

avast! antivirus - high security and protection from malware with anti-spyware and anti-rootkit software built in

Antivirus Software - Eliminate viruses with ESET NOD32 Antivirus and ESET Smart Security

AVG Free - Download antivirus and antispyware software for Windows XP and Vista

Ad-Aware @ Lavasoft - The Original Anti-Spyware Company - Lavasoft

Two really highly rated malware scanners: (disclaimer - I beta test the first app extensively, and have been for the last year).

Malwarebytes.org

Malwarebytes.org