I also use Avast, but I haven't seen this. It's entirely possible that another program is putting crap in your browser, making it seem like the malware is coming from IPS.

I also use Avast, and have not seen this issue.

I know that gravatars can give off these types of warnings. Not sure of the settings of IPS on that, but it could (could) play a role in that. 

Got this visiting a certain member page:

URL: https://community.invisionpower.com/profile/96015-jason-h/|{gzip}
Infection: PHP:WebShell-H [Trj]
Process: C:\Program Files (x86)\Google\Chrome\Application\chrome.exe

From: https://community.invisionpower.com/profile/96015-jason-h/

Then the page was blocked by Avast and says:

This webpage is not available

ERR_CONNECTION_RESET

Refresh page, still get Chrome error.

That likely happened because his profile page, Status updates, shows PHP code in one of them. Arbitrary PHP code can trigger warnings.

Thanks I'll ignore unless I think they are a threat.