Using modifications reminder list.
1.) Always backup your board and database before trying new mods. The best practice is to try them on a test board first.
2.) Try not to uninstall a modification, just disable it. Uninstalling a modification usually does NOT delete the files that you uploaded for the modification. There can be left over files on your system that alter the way your board works. (example: xml bitfield files -- which alter the permission systems of your board).
3.) If you are having problems after you uninstalled the modification. Try to reinstall it and then just disable it. This does not always work due to the programming of the modification.
4.) Still having problems. Uninstall the modification and delete all files associated with it. You will have to take a look at a copy of the original modification and find what files were uploaded and delete them. Pay careful attention with files that are stored in the 'XML' directory.
Have fun and be safe -- backup that database!