Hi, Welcome to the Forum niels1113 !
Here are all important links:
http://lmms.io/forum/viewtopic.php?f=1&t=4740
-A few rules and useful forum instructions
Yes, that happens when a VST has a flawproject won't load. It is just stuk loading this one vst instrument.
Luckily it is very easy to fix:
https://lmms.io/wiki/index.php?title=Wo ... d_problems
Just below the fix, you find a guide that will assure you never have this problem
But i am a bit disappointed. VST issues should be rare now -What version on what OS are you using?