502 Proxy Error problem

Hello All!
 
I have a problem when connecting through MS ISA proxy server.
I'm posting data:
 
POST http://212.74.173.246:80 HTTP/1.1
Host: 212.74.173.246:80
Content-Type: application/octet-stream
Connection: close
Proxy-Connection: close
Pragma: no-cache
Cache-Control: no-cache
Cache-Control: no-transform
Content-Length: 106
data...
 
But sometimes (approximately 1/2 of requests) server returns
502 Proxy Error.
 
First request passes successfully always. But next request may not pass
 and server returns error
 
What is wrong with my request?
 
Regards,
Voronkov Konstantin
ICQ 40202717

Received on Monday, 24 March 2003 10:36:08 UTC