I just recently seen that happen to someone. The only I can think of was that it was temperature related (they were both indoors and outdoors where it was snowing).

Was it the tape itself and not the splice between the leader and the tape? Find an old videotape you don't need or is already wrecked, pull a bit of tape out and stretch it until it breaks - if you can. It's pretty darn tough. Whether or not the splice failed, it must have had something to do with the temperature... but the camcorders must have been extremely cold for this to happen.

Any other details? Brand of tape, camcorders, temperature?

It was a DVCPRO M tape.

I seriously doubt it was spliced.

It wasn't that cold... just a little below zero I think.

DVCPRO 400-series camcorder I believe.

I seriously doubt it was spliced.

All tapes are spliced at the leaders...

Dunno about the rest. A DVCPRo tape is basically the same as a full-size DV or DVCAM tape. It could have been some bizarre concatenation of events (most strange things are) involving tape, camera, and conditions...

Was the tape lost, or recovered (repaired)?