Many Classic template blogs are seeing bX-sp4hmm error codes on their post pages since early this evening. Blogger engineers are testing a fix and will deploy it shortly.
We apologize for this failure in service.
Update, 10:30 PST: We had an unexpected conflict in some bug fixes to Classic template tags that caused this error. The fix for this problem is now propagating to all Blogger servers. Expect a return to full Blogger service within an hour.