oh! i just remembered.... a wild yeast can do this too. if the beer guysers and has a noticable off flavor or aroma. a wild yeast infected the secondary fermintation. if this occurs the entire batch is ruined.

this in the big breweries is called "being sewered" just dump it out. unless of course enjoy bad off flavored beer, then enjoy.

this is no joke or snide comment. but 90% of american beer drinkers can decypher a bad off flovored beer from a old aged beer. so they just drink bad beer all the time.