I don't have much knowledge of cable modems beyond the basics such as getting into the interface page and telling you what settings you might need depending on your ISP, as you say you have digiweb I would suggest trying their support page or go to boards.ie and see if you can search their forums if you have exhausted this sites info. If all else fails, Google it
My last ISP in Florida was with my local cable company and it was never a problem but then again I am not to familiar with Ireland's cable ISP's other than NTL. If you can list some of the issues with it and the make and model, I’d be happy to take a gander online.