Avira is well known for false alarms and bad performance. I would suggest that you get rid of it and get a better one, like Avast, for example.

GOG has had issues related to account hijacking. It was something to do with The Witcher 3, Galaxy, and some hackers. But they don't store any billing information so Paypal having that error would be strange.

Also, Avira sucks. Avast too. You might want to get better protection for less false positives. :P

One suggestion: If you are worried about a site being potentionally a fishing site, check the SSL information. This can be done in Chrome/Chromium by clicking the lock icon by the URL, but make sure that the URL is spelled correctly. (If there's no lock icon there, the connection is not encrypted and you should not send sensitive information to it.)

Thanks for the replies!

What worried me was I did a few orders with paypal on other sites right before checking out GOG and they were fine.
Might be something to do with the hijacking as Bunny said.

I'll wait a few days and see if it clears up ;)

You're not alone.  ;-)

Does the Avira Browser Safety addon is installed?  If it's the case, uninstall it, it's useless.  It's the replacement of the SearchFree Toolbar that was previously bundled with Antivir.  SearchFree Toolbar was provided in partnership with Ask.com, who's responsible of the nasty Ask Toolbar.

If you're using Mozilla Firefox and want to improve your security, <span class="bold">NoScript</span> and <span class="bold">AdBlock Plus</span> are better alternatives.  If you're unsure about the nature of a website, submit its URL to <span class="bold">VirusTotal</span> to see if it's legit or not.  VirusTotal is a subsidiary of Google, and it uses 65 scan engines to analyze webpages.
 
  Avast is notorious for its false positives, and Avira does a better job according to <span class="bold">AV-Comparatives</span> :

<span class="bold">False Alarm Tests - August 2015</span>
  ○  Avira:  44 false positives
  ○  Avast:  77 false positives

All AV companies are notorious for false positives. Other than that, they're only good at cleaning, never at preventing.

Agreed.

I have always been happy with Eset Smart Security, tried a few others but always went back to Eset. Never had any issues with blocking sites. I would recommend it if you're willing to pay, if not I'm sure there are other good alternatives.

Agreed.  The worst virus is sometimes the end user ( PEBCAK )  :-p

Running anti virus all the time is like having a benign virus on your computer.

This. It's a ressource hog.

We're in a era when even mobile phones have at least 2 cores and 2 gigs of RAM. I think the resource hog isn't true anymore. Even that behemoth made by Comodo was using less than 100MB of RAM when I have test it last time. Other than some increased latency, I don't think the security programs will slow anything else.

Just few weeks ago I saw some small Word document freezing my PC entirely (couple tables looped unto each other, don't ask how it is possible to do...). You are underestimating total lack of care about performance these days...

Some are worse than others. Just a few weeks ago I uninstalled Avira on my notebook and it significantly improved overall system performance. It's no highend notebook by any means (i3, 4 gigs of RAM), but it shouldn't have been performing as atrocious as it did. Took an entire minute for the OS to become responsive after reaching the desktop, because all of the trouble Avira was causing in the background.
It's would probably not be as noticeable on a more powerful system, but after seeing how it performed i wouldn't recommend that particular antivirus to anyone.