Odd Taste in Commercial Beer

I'll be honest; I'm definitely not a beer expert. I'll be brewing my first batch this upcoming weekend, so I'm a total n00b in that regard. In the meantime, I've been sampling several beers from local breweries (research!) and collecting bottles.

Two of the recent beers I've tried (Squatters' Cottonwood Amber Ale and Uinta's Bristlecone Brown Ale) have had an odd aftertaste. I can't quite put my finger on the flavor, but it's reminiscent of what wet cardboard smells like. I don't know if it was improper handling, bad batch, or just a flavor that's common for the styles (like I said, not an expert), but it's definitely a flavor I want to avoid in my brews. I know my description is vague at best, but what would cause such a flavor to be present in a beer?

Usually semen, I try to keep my pants on during the yeast pitch.............

Wet Cardboard is usually oxidized beer. Don't introduce oxygen after fermentation and you'll be fine.

When tasting beers, make sure you have a well cleansed palate. Beer and food will compliment each other with proper pairing, but some foods can make beer taste very strange. I don't know if you were eating food or drinking other styles of beers at the time, but they can both take away from the one you are trying to get a good taste of.

Thanks for the link, geer537.

Dave, I noticed the flavor on the first sip before drinking or eating anything else, but will definitely keep your advice in mind for the future.