Variable connection problems

Hi, I appear to have days when i can get 200kb speeds and days like today, when I get a persistent Error message 'unable to establish connection, check internet connection or firewall settings...' I get this message every few minutes, even when LW appears to still be downloading (albeit at a slow speed).

Some info:
Using Vista with Administrator authority
Using LW 4.12.11 PRO
Belkin Wireless Router / Zoom modem (3 years old)
BT Broadband
Windows Firewall Off
Norton Internet Security - Personal Firewall is On but LW is set to Allow
UPnP is checked
Have applied filtering as advised elsewhere in this forum
Have tried the 6346 test - it worked
Brick wall is front of the Globe all the time

Any help is greatly appreciated.
Kevin