Sandbox dialog shows up when another PC of the netwk is browsing a shared folder

I have a PC running Windows XP SP3 32bits with some shared folders.
When I browse those shared folders from another PC running Windows 7 64bits, the Windows XP PC (which is idling) randomly shows up the Sandbox dialog about some random exe file in the folder being explored by the other PC. Sometimes two or three Sandbox dialogs are shown in a row. I noticed that the dialogs use to be about the last files in the folder (alphabetically).
The PID is always 4. I checked with ProcessExplorer and it refers to “System”, from which “smss.exe” hangs. At the same time “smss.exe” contains “csrss.exe” and “winlogon.exe”.
Is this behaviour expected? Maybe Windows XP is messing something up and it’s making Avast think a file will be executed.

Needless to say, both PCs are running Avast 6.0.1000.

thanks, you’re right
– this should be fixed in next public build