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
problemgets my vote. ButerrorI'm not so sure about - maybe it would be better renamed aserror-message? – DMA57361♦ Oct 30 '10 at 15:53error-messageis not a useful tag. It in no way describes or categorizes the question. – heavyd Nov 12 '10 at 15:41problemgets my vote too, perhaps we could go through theerrortag to get a better view. – Tom Wijsman Jan 30 '11 at 13:12