What kind of beer? It's probably fine...bigger beers hold up better then smaller beers, so an imperial stout, belgian dark, barleywine beer would be better then a cream ale, blonde ale, hoppy pale ale.
Also, people mostly think that you should drink hoppy beers (pales, IPAs, Double IPAs) fresh, but I have aged many a double IPA and it still tasted great.
It can't hurt you though, just taste it and find out for certain!
To reiterate though, it's most likely just fine. Very unlikely that refrigerated beer would ruin if you haven't disturbed it, or allowed O2 into it.
First Brew was thanksgiving 2011, I'm at 52 batches and counting (as of 6/18/13), and ran out of room in my signature to list them all.