I just found the same thing using T-58 yeast. Is that what you used?
Mind, you're replying to a thread from September 2007, and hasn't had any posts since. The OP hasn't been seen here since Feb 2011, 12 years ago.
From what it looks in the pictures, there's a
pellicle floating on top of his beer, it's not mold. This points to an infection by some other microorganism that (probably unintentionally) entered when handling the beer, and took a hold.
Infections are typically not harmful to us, there not much that can grow in (fermented) beer that can make you sick. But the flavor can have changed, not often for the better, and oftentimes (some) sourness becomes present.
Over the past 10 years most homebrewers have
stopped using secondaries anymore when fermenting clean beer, as there is no benefit, but only increased risks, such as infection and oxidation.
So we simply leave everything in the "primary" until ready to package. Only if there's a really good and compelling reason we use a secondary, with the right kind of handling, which is not beginning brewer's domain.
I'm sure it's not the yeast (T-58) that caused it.
Is your beer in a secondary perhaps?
I recommend you
start your own thread, in our
Beginners Beer Brewing Forum.
If you can, post a picture of your beer as it appears in the fermenter, best without opening it, showing the issue, and describe what you brewed and how you've handled it.