Ping issue server 2008 Ent

Hello,
I want to ask you the following:
I am trying to ping the server (Win server 2008 Ent) from a terminal inside the local network with
the following command:
ping 192.168.0.50 -t -l 65500 - I am getting Request time out
If I try to ping 192.168.0.50 -t -l 32000 - I am receiving Time out again

If I try 20000 packet or lower the server is responding correctly with 4ms.
As a result, an application that usually takes 4-5 sec to load takes 40 seconds
I think the server has some kind of protection and not accepting packets > 20000 bytes
what can I do to fix this?

Also, when I ping another PC in same network with windows XP I am getting
12ms for 65500 bytes packet. So I am pretty sure is not the switch or network problems.
Also I ping the server from multiple different pc's on local network and the server is not responding
when the packets is > 20000 bytes.

Thank you in advance