No ethernet connection since recent power down

Hi,

I have an early 2008 Mac Pro running Yosemite. I connect to the internet through an ethernet cable to a time capsule, and have never had any problems until now.

I went away for a few days over Christmas, and turned off and unplugged the Mac Pro and the time capsule whilst I was away. Since I got back, the ethernet cable shows as 'not connected'. I've tried rebooting/disconnecting everything in various orders. I get the green light on the back of the time capsule when I plug the cable into the Mac Pro. I've tried both ethernet slots. The same cable works fine on another computer. I've reset the PRAM and checked all the settings which are still automatic.

Any ideas how I can fix this? Very frustrating!

Many thanks,

Stedders