Update - Draytek support provided me with a soon (I assume) to be released 3.2.4.3 version of the V120 firmware. This has cured my problems with Secondlife. The modem is now working reliably within my setup - my Linksys modem can now be retired.

Many thanks to Draytek support.

thanks for the info, found that firmware on thier dutch ftp site and it fixed all my problems