Singljohn hit the nail on the head...The only problem is that you aren't seeing the beer through it's complete process BEFORE calling what is probably just green beer, an off flavor.
It sounds like you are tasting it in the fermenter? If that is the case, do nothing.
Because nothing is wrong.
It really is hard to judge a beer until it's been about 6 weeks in the bottle. Just because you taste (or smell) something in primary or secondary DOESN'T mean it will be there when the beer is fully conditioned (that's also the case with kegging too.)
The thing to remember though is that if you are smelling or tasting this during fermentation not to worry. During fermentation all manner of stinky stuff is given off (ask lager brewers about rotten egg/sulphur smells, or Apfelwein makers about "rhino farts,") like we often say, fermentation is often ugly AND stinky and PERFECTLY NORMAL.
It's really only down the line, AFTER the beer has been fermented (and often after it has bottle conditioned even,) that you concern yourself with any flavor issues if they are still there.
I think too many new brewers focus to much on this stuff too early in the beer's journey. And they panic unnecessarily.
A lot of the stuff you smell/taste initially more than likely ends up disappearing either during a long primary/primary & secondary combo, Diacetyl rests and even during bottle conditioning.
If I find a flavor/smell, I usually wait til it's been in the bottle 6 weeks before I try to "diagnose" what went wrong, that way I am sure the beer has passed any window of greenness.
Lagering is a prime example of this. Lager yeast are prone to the production of a lot of byproducts, the most familiar one is sulphur compounds (rhino farts) but in the dark cold of the lagering process, which is at the minimum of a month (I think many homebrewers don't lager long enough) the yeast slowly consumes all those compounds which results in extremely clean tasting beers if done skillfully.
Ales have their own version of this, but it's all the same. Time is your friend.
If you are sampling your beer before you have passed a 'window of greeness" which my experience is about 3-6 weeks in the bottle, then you are more than likely just experiencing an "off flavor" due to the presence of those byproducts (that's what we mean when we say the beer is "green" it's still young and unconditioned.) but once the process is done, over 90% of the time the flavors/smells are gone.
Of the remaining 10%, half of those may still be salvageable through the long time storage that I mention in the Never dump your beer!!! Patience IS a virtue!!! Time heals all things, even beer:
And the remaining 50% of the last 10% are where these tables and lists come into play. To understand what you did wrong, so you can avoid it in the future.
Long story short....I betcha that smell/flavor will be long gone when the beer is carbed and conditioned.
In other words, relax, your beer will be just fine, like 99.5%.
You can find more info on that in here; Of Patience and Bottle Conditioning.
Just remember it will not be the same beer it is now, and you shouldn't stress what you are tasting right now.
Our beer is more resilient then most new brewers realize, and time can be a big healer. Just read the stories in this thread of mine, and see how many times a beer that someone thought was bad, turned out to be fine weeks later.http://www.homebrewtalk.com/f39/never-dump-your-beer-patience-virtue-time-heals-all-things-even-beer-73254/