If you haven't already done so, try this:
1) Shut down V4. If you're running it as a service, make sure you stop that service.
2) Delete the DB folder (default location is c:\
blueiris\db)
3) Restart V4.
It'll rebuild the database when it starts. Once it's complete, try to play a recorded clip. This solved all of my issues.
Because V3 and V4 both use the same path to save the DB files, something goes awry. Deleting the DB files does no harm since V3 or V4 will automatically rebuild them on the first start. However, repair/regenerate or compact options from within BI does not solve this problem - only deleting the folder seems to work.
Then, make sure you remove any shortcuts to V3 (if you haven't uninstalled it). It's very easy to accidentally run V3 unintentionally (don't ask me how I know). Since both V3 and V4 use the same icon, it's very easy to get burned on that.
Good luck and report back!
