This information was just posted by Trados on the TW_users list:
1) TRADOS 6.5.5 Patch Release
Online knowledge base article 1399 at: http://support.trados.com/view.asp?cntID=1399
for more information. It is a critical update for all T6.5.5 users (especially users working with non-Western languages). Besides the hot fixes, this patch enables exchanging all PowerPoint/Excel-based TTX files with users of T6.5.2 and vice versa, both in standalone and GXT/TeamWorks scenarios (see also T6.5.2 patch below for more info on this). The Public Ship Areas have been updated with these patches so that you can get the latest installers from there.
2) TRADOS 6.5.2 Filter Compatibility Patch Release
Online knowledge base article: http://support.trados.com/view.asp?cntID=1401
for more information. This patch is required for any users still on T6.5.2 that need to exchange PowerPoint/Excel-based TTX files with users of T6.5.5 and vice versa, both in standalone and GXT/TeamWorks-driven scenarios. Rather than downloading T6.5.5 (110 MB), you can deploy a patch for T6.5.2 (6 MB) before you update to T6.5.5 at a later point in time.
Make sure to read the KB articles before downloading/installing.
Best regards, Ralf