Incompatible database version

It happened to me several times by now that I get error messages related to an incompatible database version. Examples of error messages are:Error: Incorrect or incompatible database version. If you have applied any patches or hotfixes for Microsoft CRM, please apply them to this server as well.-2147467259 (0x80004005) Description: Unspecified Error.andThe version of cdf database you are