Avast has nothing to do with your fonts and I have never heard of this problem. May I ask did your new machine come with a trial version of an antivirus as most new machines do? If so, did you uninstall the trial version prior to installing Avast? The reason I mention this is because having more than one antivirus (AV) on your machine will create havoc and software will not work properly. If you are not sure if you have a trial AV on your new machine, please look at your paperwork or call the vendor where you bought the machine.
If you have another AV on your machine, let us know and we can give you the uninstaller link to remove it.
As for the WebRep toolbar, unless you select Custom Install, this is automatically installed, however you can customize things in Avast and change this. Avast is also in the process of making a fix to WebRep now, so you will see an improvement in this.
Please get back to us about a trial version of an AV on your new machine as I believe this may be causing your problems. Thank you.