Samsung Trance SCH-U490

I've had my Trance for a few weeks and I'm using a 8GB microSD card that worked great on my other phone. But with the Trance, the card seems to be causing all kinds of problems. After trying to upload music onto the card about 100 times (no joke), it seems that when I get past the halfway point of the card's memory (about 4GB), strange things happen. First, when I go to the library, the playlists just disappear for no reason. Then from that point, the phone just completely freezes and the only solution is to remove the battery.
Now I know that you may think that it's a bad card, but I get some problems with music loaded into the phone's internal memory, also. Although they don't seem to be as critical.
Whenever I call Verizon, they always ...
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What programs do I need to create a ringtone and upload it to the phone? What steps do I need to take?

It's really damn slow.