bitflipper
Note that the version 8 install requires you to uninstall your existing Ver. 7 plugins and re-scan your VSTs.

I didn't do this.  I selected the "Update" button instead of Uninstall and everything went pretty smoothly.  No problems with the new plugins here. 
 
I hope you get yours fixed ... I like the new GUIs a lot better. 
 
Cheers,
Eddie
 
 

They sure make it appear as though the uninstall is not optional. If you skip it, you get a severely-worded warning about it being "strongly recommended". Perhaps they're just being overly cautious. 
 
I went ahead and re-installed version 8 without uninstalling 7. It put me right back into the same messed-up state.
 
The suggested GPU acceleration option is unavailable because the Settings button does not get painted. I've found no obvious setting for this in the registry or any INI file. Is there perhaps a shortcut key for the Settings button?
 
This does appear to be graphics-related, because when I click on random places various dialogs pop up all over the screen, even jumping over to the second display. At one point I actually saw the "Enable GPU Acceleration" option appear, but was unable to register a click on it.
 
 
 
 
 
 

So did you ever un-install 7 before you installed 8?
After you installed 8 and opened a plug did the setup screen appear that allows you to pick a style, colors, set window and text sizes?
 
I know it kept giving my win 7 x64 fits until I finally un-installed 7 then installed 8, now all works well with the 3 Melda plugs I have. I also have Sonar x3 set to scan when I open it and I am using the VST3 versions...

I cannot find a shortcut or the GPU setting myself. Hopefully Vojtech will get back to you.

Looks like there is a reply on the Melda Forums about disabling the GPU. The reply is to a poster that is describing the same issue as bitflipper.

Yes, a very similar issue. Probably for good reason.

The solution was adding an xml file containing 
<GPU Enable="0"/>
to the folder containing the xml preset files. This prevents the GPU acceleration from initializing. It seems to be working just fine now.
 
It would be nice if he's able to figure out what the problem is because ver. 8 is more CPU-intensive than ver. 7. I opened a project that had 3 instances of MDynamicEQ. Under V7 I could enable the sonogram display on all three with no playback problems (~50% CPU), but under V8 the CPU meter jumped into the red and could not play back without dropouts if any of the sonograms were enabled.
 
Fortunately I don't use the sonogram often, but it can be handy for zeroing in on vocal resonances, which usually involve not just the fundamental but the first 3-4 frequencies of the harmonic series as well. The sonogram display makes it easy to see which ones are significant, and to precisely position dynamic filters over each of them.
 
FabFilter plugins are also GPU-accelerated, but they've never given me any trouble. 

Glad it is working for you. Too bad the feature has to be disabled; it is supposed to reduce CPU usage. Maybe it will be addressed in a future release.

See my edited post above - CPU usage is higher in Ver. 8, so it really could benefit from the GPU acceleration.