Sorry to hear about the trans, have a trans shop look at it to see if its a minor problem?
if its not, I hear that Motorcars LTD has good used ones for sale for a "reasonable" price? Aloha Alex

 

Your problem is nearly an exact description of what happened to my 2000 xj8. I bought the car in July with just over 58K on it. I have driven it less than 1000 miles and my transmission did exactly what yours did. The check engine light on my car is DTC 1722. I checked all possible causes and did the electrical diagnostics in the JTIS manual and have eliminated all possible causes except transmission electrical failure. I called around and can get a used trans with 65K installed for $1800. I have seen rebuilt ones on EBay from $1500 up. I am seriously considering listing the car on EBay with the bad trans to try to sell it. I have always wanted a Jaguar but I now realize that I made a big mistake buying this car. I have a bad feeling about this car and Jaguars in general and I think owning one is going to turn out to be a money pit. I think it is better to take the loss now instead of constantly putting money into it.

 

I would look into the transmission computer module first before pulling the trans, this may be your problem. I have no experience with them though, so I can't help you with the troubleshooting.

 

This problem is due to a stall speed failure. The problems could be low oil level, a selector cable adjustment wrong or installed wrong, an output speed sensor problem or a mechanical failure.