strange network behavior on SUSE10.3

Hi guys,
I have a SUSE10.3 server which acts as an email server and an internet gateway.
Lately something strange started happening. My internet card keeps dying after like 15 minutes, this is my eth1 which connects to the internet modem, it completely stops working, yet the LAN card is fully active and has no problem at all, i first have to restart the network service on the server for eth1 to become active again, but still yet its very slow.
Sometimes when i ping a site from that server, it brings an error

No buffer space available


Its really frustrating me and i need some help.
Thank you Guys.
Edit/Delete Message

First of all make sure that you have the right driver for your network card. Use

lspci -nn -k

and post what it says about your Ethernet cards and the modules used (relevant lines only).

Thanx for the reply, i should have added that im using an HP priliant 370MG5 server and using the Native NICS in the server.
here is the output of

lspci -nn -k

01:00.0 Ethernet controller [0200]: Marvell Technology Group Ltd. 88E8036 PCI-E Fast Ethernet Controller [11ab:4351] (rev 10)
Kernel driver in use: sky2
Kernel modules: sky2

Thank you.