Unable to monitor database storage usage

Hello,

I just updated vCenter Server from 5.5U1 to 5.5U2b. In "Service Health" there is new warning message:

"Unable to monitor database storage usage. Refer to VMware KB 2078305 for details."

I am using MS SQL 2008 R2 SP1 Express, which is supported by this version of vCenter. There is also plenty of free space on the server disk (63 GB free). KB 2078305 does not explain this particular warning message and the retention policy for task and events data is also set.

So what should be the problem ? What are the conditions to trigger this warning ?

Thanks,

  David