More problems with Smartoptimizer

I have a blog in a subdomain of my main site. Added Smartoptimizer and the css in the blog wasn’t rendering. I used this fix to exclude the blog and all seemed well. But today I went to the backend of the blog and I just get a white screen. I can’t understand why the front end would be ok and the backend wouldn’t but that’s what’s happening and I have no idea why or quite what to do about it.

Any help would be appreciated.