Hi Zilvinas,
I'm sorry you see it like that. When you guys post your questions on the forums, the questions are out of context and we have absolutely no idea what you have done and what you have not. With so many versions of VWG and users so often just installed a new versions AND cache issues being the most often hit cause for a very peculiar an unexpected behaviour in any application, even in ours when we are testing, then this sounds to me a good place to start and get over with.
When testing issues, I often test the sample application against multiple VWG versions and browsers. Thinking of recent issues, one being fixed now with the PatchTheme on 6.3.9 was tested for 5 or 6 versions of VWG to find out where it broke. In that case you can see that clearing the cache must be included in the standard procedure used for switching versions, so we do it all the time ourselves.
Unless the user explicitly states that he has just followed that procedure to clear the cache, we simply need to know...
Tell us that you JUST followed the clean cache and reregistering DLL's in your every request (and mean it) and I promise I will stop asking you to 
Palli