The glossary page will give exact definitions of each defensive stat:
Out of the Park Baseball Manual
I am no expert on the specifics, but I know that no single stat is the final authority on describing the total picture.
In your shoes, i would first want to know whether my team has a fielding problem... Is the team ranked significantly worse in giving up runs than in ERA?
If you are ranked higher in runs allowed, your fielding is helping you. If you are ranked worse, your fielding is hurting you.
If there appears to be significant fielding problem, I would ask whether this might be a temporary blip. How far into the season are you? Early May -- I'd suspect low sample size. Late August -- I'd look into the matter carefully.
Next, I'd look into some isolated statistics more closely. For each position on the team, where does my starter rank against the rest of the league? Fielding percentage, double plays, range factor, zone rating, errors, etc.
At the same time, keep an eye out for the possibility of a couple reserve players whose stats are so out of line that even in a supporting role, they are playing havoc with overall results.
Don't forget to check pitchers' fielding, too.