Error -12263 with 2checkout module- not returning - anyone seen this ?

Hi:

I've upgraded yesterday my website to the latest zen cart version 1.3.7.

I've installed the 2checkout module, modified database and changed carefully all settings at my site admin and my 2checkout control panel as per instructions.

However I'm getting an error and customers are not returned to my site.

Return doesn't work , neither manually ( auto return off) by clicking the continue button, neither automatically ( auto return on)

when I try manually to continue with autoreturn off I'm getting a pop up notice that says

" thailandhandicrafts.com has sent an incorrect or unexpected message. Error code -12263 "

Actual payment does come through !!!!

I've removed and reinstalled several times the 2checkout module and still is not working, what could be wrong ?

why is not returning

Anyone seen this error before ?

Please help !!!

many thanks

I am also getting this error in shopping cart. I can't even log into my Admin. I do not have 2checkout, but I get the same error code.