I know, there are many problems backing up 2007 Exchange with Backup Exec 12.5
I had many customer support calls for that issue, and did (I think) every troubleshooting tip you can imagine.
Also involved Sym Adv. tech support, which finally came to the solution, that we should check back with MS support to get the VSS problems with 2003 Server and Exchange 2007 solved.
Like you noticed, this all took place because problems backing up Exchange 2007 on Server 2003 occured.
Now I set up a new test environment to verify a customer support call and noticed, that I also receive VSS Writer related backup errors.
The same errors I already know from the other calls, but now on a Exchange 2007 on Windows 2008.
As far as I know, there is no possibilty to update a Exchange 2007 SP1 on Server 2008 further. No VSS Updates, No Service packs, no more hotfixes.

The Fact:

A full GRT backup of the Exchnage to a local disk of the backup exec server fails with the following error, over and over again

0xe000fed1 - A failure occured querying the writer status
0x800423f3 - The VSS writer failed

We all know this error codes I think, but now I am nearly at the end of my ideas.
Did anyone manage to backup a Exchange 2007?
Any tips for me?

btw: Media Server is also a 2008 Server

This really gets annoying, as these problems and the associated support calls from customers grow with every day...

Thanks in advance!