Have many EX-1 projects going, all was fine. I may have accidentally changed something.
No matter where I put the play head, audio is in sync for a second, then falls out. Could it be a sequence setting?

There's nothing inherently wrong with EX and sync so you must have done something but there's no way anyone here can guess.

Create a new project using EX easy setup and put your files in there. Create a NEW sequence and see what happens.

Have many EX-1 projects going . . . No matter where I put the play head, audio is in sync for a second, then falls out.

Does this happen on all your sequences, or just one in particular?

What is EX easy set up? And, yes, it happens on all sequences.

This problem must be very frustrating indeed. I know because I had a very similar experience with the Panasonic HVX200. FCP didn't fully support the format I was using.

The good thing about it was it prompted me to change to the EX1 and that was an excellent move.

Unfortunately, people can't answer your question if you don't provide information for them to trace the problem from.

What editing system are you using?
What system version (and has it been updated recently)?

Are the sequences that you say were previously in sync, now going out of sync?

What format are you shooting?
What format are your timelines?
(In FCP you should use Easy Setup to make the project the same as the format your footage was shot in, then open a NEW sequence and drop the clips in there).

Lastly, what is your exact workflow?

Got it, used EASY SET UP, and chose XDCAM EX 1080i60 VBR. Can someone confirm if this is correct? Material was shot in 1080i60. The pull down menu was on something else I can't remember now.

used EASY SET UP, and chose XDCAM EX 1080i60 VBR

Sounds right but I'm in PAL territory, so I can't be certain.

Is the audio back in sync now?

Yes, most definitely. Thanks for the good advice.