Hello scrumdown! I too had a similar issue with Avast Online Security with IE10 which caused IE10 to load it’s homepage google.com really slow, but opening IE10 is fast. Back then I had avast 2014.9.0.2006, I then reported this issue to Avast. When they came up with their reply, Avast 2014.9.0.2007 was released and then the issue automatically was gone and I told them it’s fixed by the new release.

If you are still facing this issue, I suggest you uninstall your current version of avast by add/remove and run http://www.avast.com/en-nz/uninstall-utility.

After that download and install a fresh install of Avast. After installing it, avast will do a startup scan. After that has been completed register your Avast antivirus and restart your computer again.

Since you are using IE10, IE 11 got recently released. I suggest you install IE 11.