At a client, the Team Foundation server 2010 environment was working fine until suddenly the Sharepoint stopped working. In the event log, I found the following error message:
The schema version (3.1.8.0) of the database SharePoint_AdminContent_d3718c5d-5516-41e1-ba7d-6e5a3c21ba75 on DatabaseServerX is not consistent with the expected database schema version (3.1.11.0) on ApplicationServerY. Connections to this database from this server have been blocked to avoid data loss. Upgrade the web front end or the content database to ensure that these versions match.
I found out that Windows Update had installed some patches which upgraded the Sharepoint application front end to a higher version. Unfortunately this made the front-end and the underlying database incompatible.
I fixed the problem by executing the following commands on the application server:
1: stsadm -o upgrade -inplace -url <central admin url>
2:
3: iisreset