Hi,
Do these to clear corruption and repair/replace damaged/missing system files.
Run DiskCleanup - Start - All Programs - Accessories - System Tools - Disk Cleanup
Start - type in Search box - COMMAND find at top of list - RIGHT CLICK - RUN AS ADMIN
sfc /scannow
How to analyze the log file entries that the Microsoft Windows Resource Checker (SFC.exe) program
generates in Windows Vista cbs.log
http://support.microsoft.com/kb/928228
Then run checkdisk - schedule it to run at next start and then Apply OK your way out then restart.
How to Run Check Disk at Startup in Vista
http://www.vistax64.com/tutorials/67612-check-disk-chkdsk.html
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Then lets refresh the USB Stack
Control Panel - Device Manager - USB Serial Controllers - RIGHT CLICK on EVERYTHING and UNINSTALL
all except the category itself - REBOOT - this refreshes the drive and the USB stack
This KB shows the XP how to and the Vista method is identical
http://support.microsoft.com/kb/310575
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If needed try both of these :
Tips for solving problems with USB devices - and a Mr Fixit
http://windowshelp.microsoft.com/Windows/en-US/Help/c39bd203-f729-47a4-8351-83291e13c8a81033.mspx#EGB
Hardware devices not detected or not working - Mr Fixit
http://support.microsoft.com/gp/hardware_device_problems
Hope this helps.