I think I've found a solution to all the VAB crashes.
I run KSP through steam and noticed that when you uninstall the game many of the game files still remain in the steam client.
What I did was uninstall the game on steam and then manually delete the "Kerbal Space Program" folder in the steam client.
which is located here :- C:\Program Files (x86)\Steam\steamapps\common\
Another thing I noticed was that steam automatically starts KSP in 32-bit mode but you can start in 64 bit mode by clicking on KSP_x64 at the above address.
I was experiencing VAB crashed every 5 minutes. I just ran KSP for an hour in the VAB with no crashes so I'd be interested to see if following this procedure makes any difference to anyone else.