We have 2 proxy servers. One always displays the page correctly, the other sometimes changes page layout (fonts are not displayed correctly and certain backgrounds/layout/formatting are missing. When this happens on proxy server 2 and we press CTRL+F5 in the browser the page displays correct the second time. When we close the browser and go to the page again the same happens, and again it is correctable by pressing CTRL+F5. This does not happen to all the pages, but among the sites that are displaying this symptom on proxy 2 are www.hp.com and www.microsoft.com

What might be causing this issue on proxy server 2?
Where should we start the troubleshoot ?

Proxy server 1 (display is always correct):
Netware 5.1 SP8 + latest TCP stack patch
Bordermanager 3.8 SP4 (proxy 071)
HP Proliant DL380 G3
2 GB memory
Dual P4 2,8 Ghz
Gigabit NIC
2 Mbit internet connection.

Proxy server 2 (display/layout is sometimes wrong):
Netware 6.5 SP5
Bordermanager SP4 (proxy 071)
HP Proliant DL380G4
2GB memory
Dual P4 3,2 Ghz
Gigabit NIC
100 Mbit internet connection.

Kind regards,