Here are all important links:
http://lmms.io/forum/viewtopic.php?f=1&t=4740
-A few rules and useful forum instructions
Are you using MAC? VST does not work there yet
IF OS not MAC
please post your:
* OS (+service-pack-version)
* lmms version
* hardware specification (ram & soundcard is the most important)
* Name of VST involved & link to a download for this VST
Also
try MDA-Piano http://mda.smartelectronix.com/synths.htm
It is very small in size, and you can just copy it to your folder. -Eg NO installation! Further its a quite good piano-instrument, so it is a win win
Let us know the outcome :)