Brent Daley offered this tip: "When you get a lot of xrefs into your drawing, your layer list can populate with well over a thousand layers. Then your layers can get mixed up in your pull-down list. The MAXSORT system variable sets the maximum number of items sorted in a list. The initial value is 1,000. If you find you are having a problem with your layers being out of whack, bump this number up to 5,000."

NOTES FROM CADALYST TIP PATROL:
The maximum for the MAXSORT system variable is 32,767. A value this high shouldn't be a problem for today's high-speed computers. With drawings becoming more and more complex, this is a good reminder. Thanks, Brent!