Problems with Samba and Roaming Profiles (Samba3.3.9 & Win7)

[ReggieW]

We have a server running Gentoo64 with Samba, it's acting as a PDC. All clients are using Roaming Profiles and have joined the domain.

The clients are running on WinXP(32-bits) and Win7(64bits), at WinXP everything works perfect.

At the Win7 clients we are using Outlook and Thunderbird, connecting to a IMAP server.
When the users on Win7 are trying to open attachments like pdfs, docx, jpgs then they are corrupted at the most of the time,
it looks like the profiles aren't saved correctly to the server. We have tested multiple of possible solutions for Thunderbird
but none of these worked. The same problems occur when you try to open the same attachment in Outlook

We have tested a clean installation of Win7 without joining the domain, we have only setup the workgroup. This doesn't give any problems with the attachments.
Probably theres something wrong with the synchronisation of the profile(s) to the server.

Samba version: 3.3.9
Gentoo64: 2.6.34-r12
Outlook version: 2007
Thunderbird version: 2.0.0.8 - 3.1.10 (tested versions)