Here are all important links:
http://lmms.io/forum/viewtopic.php?f=1&t=4740
-A few rules and useful forum instructions
"The update" Do you mean from LMMS1.1.3 to LMMS1.2.0? That should only give you issues, if you install 1.2.0 in a different folder, than your 1.1.3
Are you attempting to have both installations? Dont do that 1.1.3 is inferior.
You will get issues, if you installed on a new pc, and or different folders, then you need to reset your path's in Settings
Go through all the path in Settings| Directories, and make sure all links correspond to your actual file-folders
(All issues can be avoided if you as a new user always install in the proposed default configuration)