Hi,
We added the messagebox several versions ago, to notify that the PKCS#11 dll is not found.
1.5.1.2 still showed that message box. Are you sure you were using 1.5.1.2?
Anyway, now we just discussed about that and we decided to remove such messagebox to allow more complex algorithm for loading PKCS#11 dlls.
We are going to release a new version that removes such messagebox throwing only the exception.