I was involved in a project to apply a maintenance release to an existing Lotus Domino installation running on Windows Server 2003. The goal was to upgrade the server from version 6.5.5 to 6.5.6. During the upgrade process, the installer checks the version of Domino that is currently installed and makes sure you are running a version that is compatible with the incremental update. The installer kept reporting to us that it could not continue with the install because we were running 6.5.5 and 6.5.5 was required! When digging through the upgrade.log file, we found the following error:

The file lnmibdll.dll is missing or in use by another process.

We were confident that the file was there, so the real trick was figuring out which process was using the library. We shut down the Lotus Domino SNMP Agent, but this had no effect on our install. In the end, we discovered the SNMP Service and the lock on lnmibdll.dll was released.