The Exchange team put a notice up today on their website on an important update for Outlook 2007 regarding personal archive support on Exchange 2010. Unfortunately, the post doesn’t contain any information regarding the issue itself, only that it may result in inaccessible archives. The fix will be included in the February 2011 Cumulative Update for Office 2007, which is to be released later this February.
This Outlook 2007 personal archive support is becoming some story. After the the initial update enabling this functionality, Outlook 2007 Cumulative Update of December (kb2412171), the update was re-released in January to include 3 fixes (see kb2485531). Now we can expect another fix for an undisclosed issue.
I suggest keeping an eye on the Outlook team blog for updates regarding this issue.