I have used many brands of sanding belts over the years.  The best buy
I have found on the 6X48 belts I use is from Grizzly Industrial,
http://grizzly.com/  A 10-pack of aluminum oxide belts runs about $35,
Klingspor about $80.  I've had no trouble with them breaking or
wandering, and last about as long.

Brian Thornton - Short Mountain Music Works
Woodbury, Tennessee
http://www.shortmountainmusic.com/