I think i know the cause of this...
I have also Panda USB vaccine.
@david,
1. Try inserting a USB flash drive.(Behavior shield detect USBTOR.sys as suspicious but no pop up.)
2. Remove the USB flash drive.
3. After restarting the system this pop up appears.
Avast all scan logs
Mbam Scan Latest version and updated
Malwarebytes' Anti-Malware 1.51.0.1200
www.malwarebytes.orgDatabase version: 6751
Windows 5.1.2600 Service Pack 3
Internet Explorer 7.0.5730.13
6/2/2011 10:45:58 AM
mbam-log-2011-06-02 (10-45-58).txt
Scan type: Quick scan
Objects scanned: 143441
Time elapsed: 3 minute(s), 9 second(s)
Memory Processes Infected: 0
Memory Modules Infected: 0
Registry Keys Infected: 0
Registry Values Infected: 0
Registry Data Items Infected: 0
Folders Infected: 0
Files Infected: 0
Memory Processes Infected:
(No malicious items detected)
Memory Modules Infected:
(No malicious items detected)
Registry Keys Infected:
(No malicious items detected)
Registry Values Infected:
(No malicious items detected)
Registry Data Items Infected:
(No malicious items detected)
Folders Infected:
(No malicious items detected)
Files Infected:
(No malicious items detected)