[cdw334]

I have a Frigidaire refrigerator with a water filter dispenser/ice maker. The filter catridge currently in it has been in there for about a month or two, no problems. Now all of a sudden, every now and then the water tastes awful like it is clearly straight from the faucet. I take the catridge out and slam it back in, run water through, and the next taste is beautiful again. I don't want to keep gulping down water only to realize when it's too late that it's unfiltered filthy faucet water. My trust in this filter if dwindling. What is going on? Is this a problem with the catridge or with something in the refrigerator? Is the water simply bypassing the catridge? From looking at the things inside it, it doesn't look like it's possible but I don't know anything about it. Here is a picture of the catridge...
http://img710.imageshack.us/img710/6919/001vpc.jpg
Please help! Any help would be much appreciated, thank you.