Update: Meanwhile there is a further Februar Rollup available:
Description of the System Center Virtual Machine Manager 2008 R2 hotfix rollup package: February 9, 2010
Please note that when you installed the Rollup, you need to allow the Host agents to be updated, as described here:
Recently we published a Rollup Fix for System Center Virtual Machine Manager 2008 R2, and an Update for the Management Console on Microsoft Update.
Description of the System Center Virtual Machine Manager 2008 R2 hotfix rollup package: November 10, 2009
When you remove a virtual hard disk from a virtual machine in System Center Virtual Machine Manager 2008 R2, the .vhd file on the Hyper-V server is deleted without warning
When your SCVMM Server or Admin Client is not directly connected to the Internet you may have the need to download the package from another machine
You can get the fixes from http://catalog.update.microsoft.com and specifying Article 976244 and/or 976246.
You’ll get .cab files containing .msp files which you can install from an elevated Command Prompt.
To install the Server rollup specify:
msiexec /p vmmServer64update.msp BOOTSTRAPPED=1
To install the Client rollup specify:
msiexec /update vmmClient64Update.mspBOOTSTRAPPED=1
or, if your Admin Machine is 32bit:
msiexec /update vmmClient32Update.mspBOOTSTRAPPED=1