@ClassyJakey,
There is relatively a simple solution. Download the latest stable version of avast, of the same edition (Free / Pro / AIS) you are currently using. If you are using Pro / AIS, download its latest stable Trial.
Close any other applications and run the new setup.exe (over the current avast; NO need to uninstall first). Once finished, wait until the HDD led is no longer blinking "like crazy" (only normally). Is there any messages about system changes? Allow system changes, and *then* click on "reboot now -> yes" (the end of the installation process).
After the reboot, let avast start normally (don't "rush it"). Is it working correctly now? Please report back.