I haven't been out to the customer yet, but they called reporting that they can hear each other talking occasionally while on a call. Classic crosstalk I think, but has anyone heard of this on the Panasonic?

I'm not aware of any specific problems and there hasn't been any tech. bulletins out on this type of problem.
I really doubt if it's in the system.
your going to have to go on site and investigate.
Is it between extensions, 2 of their COs or 1 co and an outside sorce? If it does point to after the system it's usally a cabling problem.
You'll have to track it down a bit, once you have somthing definate re-post and we'll go from there.

I'm having this problem as well. I had a phone tech come out to take a look at my cabling, and he said it's all correct. I'm running each CO line from the phone box on the side of my house into the house on its own Cat5 cable. Each cable goes directly into the CO lines in my TA308. I'm getting cross-talk between my two CO lines something aweful. I have the TA308 grounded very well. Since the Cat5 cables are shielded and I'm using a separate Cat5 for each line, it can't be cross-talk along the way from the phone box to my TA308. Any suggestions are appreciated.

Although I really don't think that shielded Cat5 is necessary do you have the shields all tied together and grounded at 1(and only 1) point?
I really believe it's coming from the CO.
Sometimes it's hard to pick it up on an slt or buttset as there generally more forgiving then a switch or ksu which could actually be amplifying
the problem.
who is the CO provider?
You may have to just keep reporting it until you get a Tech. who's willing to check the line current and loop resistance coming from the CO. They can also check for continuity between pairs. The real problem may be getting someone to do this.
If you complain enough they will probably change the pairs to the NID or D-marc.
Good luck.