No. I thought you might have removed it to clean it and then failed to reattach it properly.Hmm, no I left the tap on when sterilising. I filled it to the brim and left it a day (then cleaned it out). No leaks at that point, so rinsed it out and filled it with beer.
Could the steriliser have damaged the tap?
I think you probably had the same problem as AcidHell2 ("I had that on my king keg. It didn't come tight enough"). You could try syphoning the beer back into the fv (be sure to sterilise first) and then see if you can fix the tap, or get a new keg, or bottle it. Might be worth asking here first - http://www.brew-it-yourself.co.uk/forum/phpBB2/index.php.
Good luck.