The VSTi in question is Tapeworm by Tweakbench.
It used to work fine but all of a sudden (with no changes to my DAW) I'm getting the error messages below when trying to load it. Anyone have any clue to what the problem is?
I'm using Sonar X3, Windows 10 - 64 Bit
 

This is an old SynthEdit plug-in. When the plug-in is first loaded it needs to create a folder and write out several support modules. I believe if you run SONAR as administrator once and load the plug-in, it will have the chance to create the files it needs. Alternately, changing the permissions on the folder containing the tb_tapeworm_2_1.dll granting users write access will do the same thing. Either way, once tapeworm writes out the SynthEdit support files into a tb_tapeworm_2_1 folder where the tb_tapeworm_2_1.dll is located, the messages should go away.

scook
This is an old SynthEdit plug-in. When the plug-in is first loaded it needs to create a folder and write out several support modules. I believe if you run SONAR as administrator once and load the plug-in, it will have the chance to create the files it needs. Alternately, changing the permissions on the folder containing the tb_tapeworm_2_1.dll granting users write access will do the same thing. Either way, once tapeworm writes out the SynthEdit support files into a tb_tapeworm_2_1 folder where the tb_tapeworm_2_1.dll is located, the messages should go away.

Thanks for the reply - I ran Sonar as administrator and Tapeworm loaded okay when I did that, but when I went back to opening Sonar as normal the problem came back.
The folder with the support modules has been created but the messages are still popping up as before.
 

It seemed to work OK for me once the files were created but I did not test it very extensively. You may need to run SONAR as administrator from now on. Relaxing the permissions on the support folder and files might work too. There are alternatives to a synthedit plug-in for mellotron like sounds.