BorderManager 3.6 SP1a running proxy.nlm from BorderManager 3.7Sp2

On some websites we sometimes experiance very slow loading times. When

hitting F5 to refresh the screen the pages loads at once. Seems like
download process is stuck for some reason and doesnt complete.
This behaviour is "normal" since we set up the servers, so it is not related to a specific patch or the proxy.nlm version.

Also i have a problem connecting to this website:
getting a "No Service Name Specified" error website. Cookies are
on the workstations and i also tried to set these web sites as "Non
cacheable URLS" but this didnt help.

Persistent connections to browers and servers are enabled.

Thanks for any ideas or suggestions i missed so far...