There is a .NET CLR hotfix that has just been released and which is recommended to be applied on every Exchange 2007 server. It is more urgent to apply this on CAS servers with multiple protocols to reduce the memory load noticed on CAS servers with other roles, but in general it is recommended to be applied on all Exchange 2007 servers.

The KB article to reference is http://support.microsoft.com/default.aspx?scid=kb;EN-US;942027.

And finally we released our Exchange 2007 management pack for OPS 2007

 you can download it from here http://www.microsoft.com/downloads/details.aspx?FamilyId=1A83E112-8677-4E03-83C3-F1B7EBFC3A4B&displaylang=en

Enjoy,