Thank you! I am running (stable) 2.1.4 of JForum and I recently needed to upgrade MySQL to the 4.1.x version. I fixed the first problem with the encoding formats. However, almost immediately after that I hit this problem.
After seeing your post I checked there and found the solution. For anyone else that needs the fix, I'll post it here so that it's more clear. You must replace your mysql jdbc driver in the JForum package, which is the following file:
Delete that file and replace it with the older 3.0 branch of the driver from the MySQL site here.
I used version 3.0.17 and this fixed everything for me. Just unzip/untar the download, and copy the file "mysql-connector-java-3.0.17-ga-bin.jar" (or similar version) into your"jforum/WEB-INF/lib" directory. Again, if the other file is still in there ("mysql-connector-java-3.1.4-beta-bin.jar") just delete it. Then restart your application (or container). Everything should then be working properly. [originally posted on jforum.net by fcgreg]