Does your Speedtouch modem have the capability to be installed by either USB
OR Ethernet, or is it purely a USB modem? If it has both ports on the back, try uninstalling it all and re-installing using Ethernet. In my experience as an IT Technical Analyst, Ethernet is far more stable and reliable than USB.
It's just an idea, but you never know, we may just hit an idea that resolves your problem.