Yesterday I was working on a DPM installation and made a mistake when I was working on a protection group and I needed to change the size of the allocated storage.  I made the mistake by lowering the size and pressing the TAB button and suddenly the DPM console crashed.  Here’s what I did:

Go to the DPM Console –> Protection.

Choose the correct protection group and press the Modify Allocation button.

Press the Calculate button

After this, I changed the size of the replica to 10 GB and pressed the tab key.

Et voila,

Till now, this bug is confirmed by Microsoft and not yet solved… ;-)

http://support.microsoft.com/kb/973677

Read the complete post at http://scug.be/blogs/scdpm/archive/2009/09/02/system-center-data-protection-manager-error-when-lowering-the-allocated-storage.aspx