"Default gateway not available" - Internet connection problems

Hi All

I've had Windows 7 for about 6 months, and have been getting an intermittent problem where my internet cuts out. The network icon shows a yellow exclamation mark and I have to right click on it and Troubleshoot Problems, which then resets/repairs the connection and everything's okay.

Here's some details from the troubleshooting report:

Network adapter Local Area Connection driver information:

Description . . . . . . . . . . : Realtek PCIe GBE Family Controller
Manufacturer . . . . . . . . . : Realtek
Provider . . . . . . . . . . . : Microsoft
Version . . . . . . . . . . . : 7.2.1127.2008
Inf File Name . . . . . . . . . : C:\Windows\INF\netrtx64.inf
Inf File Date . . . . . . . . . : 13 July 2009 20:37:30
Section Name . . . . . . . . . : RTL8168D.ndi
Hardware ID . . . . . . . . . . : pci\ven_10ec&dev_8168&rev_03
Instance Status Flags . . . . . : 0x180200a
Device Manager Status Code . . : 0
IfType . . . . . . . . . . . . : 6
Physical Media Type . . . . . . : 14

I've found some posts on the net about this problem, and people have said it's a known issue with nvidia, but my network controller's Realtek.

Anyone have any experience of this?

Thanks in advance
Chris