Ok, so i'v checked in the BIOS. All of the 'Wake on...' options have been set to disabled, and i'v set the 'Suspend mode' option to S3. I'v also gone onto device manager, selected my network adapter, and made sure that the 'Allow this device to wake the computer' option is unticked. However, the problem still occurs. I have to say i'm stumped!
The only solution i can think of is updating the BIOS, as i don't think i have the latest version; but even so, i don't think it will make much difference.
Does anyone have any more ideas?