Cubase 8 Crashes (on Boot) after Install of G A 4

I downloaded and installed Groove Agent 4 and since then every time I try to boot Cubase it crashes straight after I click on the file (existing song, any of them). I have un-installed/reinstalled Groove Agent 4 twice more but it makes no difference. Up until then everything was running smoothly with no noticeable problems.

System: iMac Retina 5k 27’ (late 2014), Intel i7 4Gig, 24gig 1600 Mhz DDR3 RAM, Yosemite 10.10.3
Interface: Yamaha n12 mixer/Interface with the latest drivers
There are only music programs on this Computer and as I said everything was running very well before the download and install.

Ok, I (for the third time) trashed the preferences and this time for some strange reason it seems to have cured the problem. So to summarise, I tried to re-install Groove Agent 4 (twice) which didn’t work, I then Un-installed a synth (software) that I thought might be the problem, and now I trashed the Pref’s again, and it seems to have worked. I shall report back if I find any further info. Thanks Everyone…Oh yeah nobody replied, ha ha Ah well, as we say here in Australia, “No Biggie” (means no big Deal!)