W explorer freezes once !

[Crios]

Hi

System:
W XP SP3 (updated),
1 USB external HDD (Samsung Story Station 1.5 T), AV: Avast Pro 4.8
Updated

Windows explorer freezes the first time I try to use it after I open the
computer (I have "Restore previous folder window at logon" option checked),
regardless the drive I use (int/ext HDD, flash).

Windows Task manager shows "Program not responding" and I have to End the
task.

After I open W Expl again (Win key+E) everything runs normal (rarely it
freezes twice).

I scanned the computer and I found no viruses.

Advices ?

Thanks
Crios