Hi,
I was also facing the same problem that if the data being sent to the client exceeds certain limits then the data comes scrambled.
I used the fiddler tool to analyze the problem what I could see is after some limit (for me it was 8000 chars in responseText) the problem starts. Within that limit things work fine. I cant say that data is cut off because in fiddler I could not see the data what has been sent, it is some different irrevelant text.
It would be great help if somebody can solve this problem.