5
This is the first I've seen your posts on this. Things get buried fast when you're not online..
Does this error appear when you save/edit a block? I remember seeing that in pre 2.0.9.2 versions and thought that as a nuisance error since the cache was actually working.
Of course you should double check that /cache & /templates_c is chmod to 777. Wouldn't hurt to manually empty those directories (leave /templates_c/index.html) and then watch those dirs to see the new files appear.