Strange. If you delete the whole "chain" folder does anything different happen?
Slightly different. First time I did it last night I got the blue screen and 'bitshares starting', which wasn't happening before. That stayed for about four hours and then I had to power down. Today I get the bitshares starting screen flash for a second or two and then the same critical error message.
Also in the command prompt, I get the same thing as above but also this bit, which I don't remember seeing before:
th_a fast_level_map.hpp:64 bts::db::fast_level_map<unsigned char, struct bts::blockchain::property_record>::toggle_leveldb