ZBrushCentral

Geometry HD issue

I’m having a prob with HD sculpting… I’ve been using Geometry HD to get finer details in my Terminator model. I’m up to 419 million polys without any problems so far. I’ve been saving my Ztool every 10 mins or so. After about 14 hrs of sculpting these fine details. I took a break and shutdown my comp to give it a rest. When I loaded my Ztool back into zbrush everything seems fine, when I hit sculpt HD. The mesh literally Explodes where I sculpted previously on the HD mesh. All other parts untouched by the HD sculpting is fine.

Any ideas on what the hell happend?
If so how do I fix this?
lol that would suck If I have to go back to a previous save of it, but if I do I hope I can avoid this error in the future.

Thanks alot for any help recieved =]