Vienna Instruments Pro seems to have major compatibility issues with Cubase 8. Cannot playback multiple instruments such as Dimension brass "all" Matrixes after recording or saving project. This only seems to happen though when Vel.XF  is switch on. Have tried many newly created projects under both 8.0.20 and 8.0.30 with all the same result. I then tried the same project in Cubase 7.5.40 and it seems to work fine again. Also works OK when using VIPro in Ensemble Pro and Pro Tools. Strange thing is that the track(s) seem to playback OK in Cubase 8 as long as it remains record enabled. However, disable record on the track and try to play it back while Vel.XF is turned on and forget it. Performance meter immediately jumps into the red. Keep in mind this is only playing back a single midi track. I also tried re-installing Vienna Instruments (free, standard edition) with the same results whenever Vel.XF is switched on. I also tried trashing all preferences temporarily for both VSL and Cubase 8. No change! Not sure what the problem could be but it is definitely not compatible with Cubase 8 on the Mac (see specs below).

Mac Pro (Mid 2012), 3.2 GHz Quad-Core Intel Xeon, 32 Gb Ram

OSX Yosemite 10.10.4, Cubase 7.5.4 and 8.0.2/3, VEPro 5.4.x, Pro Tools 11.3.1

Actually, not such a wild guess. That seems to have done the trick. Disabling ASIO-Guard immediatelty seems to have brought everything back to normal. Turning it on again completely screws everything up. Not sure what the probelm is but seems like not many third-party plugins are not compatible with this ASIO-Guard feature. Not sure why Steinberg even bothers keeping it in the program. Strange thing is that ASIO-Guard is in Cubase 7.5 as well, and yet it doesn't seem to have the same issues. Steinberg had to have made some major changes in version 8 in order to have caused all these problems. This would be typical of them. Cubase has some great features but has always been known for buggy software, especially on the Mac platform.

Thanks.....

KM