From http://blog.stackoverflow.com/2010/08/the-death-of-meta-tags/:
If the tag can’t work as the only tag on a question, it’s probably a meta-tag.
If the tag commonly means different things to different people, it’s probably a meta-tag.
error is more for error messages, so no, but...
problem is more subjective. What may be a problem to some people is a benefit to another.
There are currently 170+ questions tagged problem
problem
gets my vote. Buterror
I'm not so sure about - maybe it would be better renamed aserror-message
?error-message
is not a useful tag. It in no way describes or categorizes the question.problem
gets my vote too, perhaps we could go through theerror
tag to get a better view.