There have been a lot of failures of the VDSL modem - I'm on my second. In my case there was little warning of any problem (played up a bit one Sunday, died totally the next day).
The problems might (or there again might not) be related to overheating.
If your current modem is working OK then a new one probably won't "improve" things.
Do you know what your connection speed is (the IP profile speed reported by the BT speed test)? Or your sync speed?
Edited by mr_bean (Fri 11-Nov-11 12:45:25)