About my Swisher Z-Max ZT2660B...I was mowing, and suddenly the blades just stopped turning. No warning of any kind, engine still running. Any answers out there?

Swisher is proprietary in the service arena for information. The most common cause of the issue that you are describing is belt slippage. This could be due to oversize belt length. improper tension, loose pulleys etc. Also when you look at an area that you have mowed after one day, if the tips of the grass are yellow, the blade is not sharp enough.

sounds like a faulty safety switch

Your idler pooly is the culprit. The idler pooly should have no kind of play at all. Rock it up and down if it moves replace it.

http://www.swisherinc.com/media/documents/ONZTR42_REV_02_01_2002.pdf

I have this mower and had this same problem. It turned out the bolts holding the motor to frame backed out and were allowing the motor to tilt, and then the belts would slip and burn up. Check all motor bolts for tight, and if not tight change bolts and lock washers. Lock washers were not originally on these mowers.

Even though the routing is correct, have you checked that every spindle and idler pulley turns freely? These bearings can freeze up or bind because debris builds up in them. Also, if the bushings on the idler pulleys can wear, causing them to misalign. Keep checking. Also - is the belt snapping clean, or do you see a burnt, worn spot?

the one thing I have noticed with my swisher 60" is my grass have to be dry or the deck will clog and because of the mulching deck it is not recommended to cut tall grass.

drop the deck and check all of the moving parts. you have a part that is frozen up, maybe a single blade pulley wheel which is causing this.

This actually happened to a friend of mine! I saw it! Mow about 20 feet, and had to stop, then 20 feet...well, you get the picture. It was his air filter! Stopped up pretty good. We blew it out and it worked fine.
I really hope this helps. --W/D--