Avast 5 mail sheild with outlook express corrupting publisher files

Using outlook express 6.0.2900
avast 5.0.545
xp pro sp3

when we send .pub (ms-publisher 2003) attachments they arrive corrupted
likewise when we receive .pub attachments.

.xls, .doc, .pdf, .ppt are all ok… just an issue with .pub files.
If I disable the inbound and outbound mail sheild, then attachments are fine.

I’ve tested the same scenario on win7 with outlook 2007, publisher 2007 and it’s fine.

so is this a known issue?.. and is there a fix other than disabling mail scanning?

windows live is an option I guess.