"Security Alert" in all pages!

[Oscarito]

Hello fellows!

Since the last update I'm receiving "Security Alerts" in ALL loaded pages from Internet. I've already uninstall/reinstall "AVAST free" twice but problem remains. How could I solve this annoying phenomenon?

Thanks in Advance!

EDIT: I'm performing some tests, and I don't have such alerts when the AVAST is uninstalled...

[CraigB]

What are the alerts saying, a screen shot would be good if you can.
To add a screen shot use the option ( attachments and other options ) which you'll find at the bottom of where you write your post, try to only include the neccessary information in the shot so you dont go over the allowed size limit.

[Oscarito]

Here it is!

Sorry, it's written in Portuguese. I'll translate for You.

"Security Alert
Do you want to show just the content offered in a safety way by this Web page?
This Web page shows content that is not offered by a HTTPS conection, which may endanger the hole page.
-More Information-                 -Yes-               -No-"

 

[CraigB]

The alert has nothing to do with avast, more to do with the security settings of your browser i believe.
Can you use the information drop down to change it to always use http rather than https, im not to familiar with xp anymore these days and avast doesn't scan https.

[Oscarito]

Well OK, but as I've said before these warnings don't appear when AVAST is uninstalled, and this not happened with the former AVAST version. No browse settings changed. I've asked about a solution in some forums but none of the suggestions succeded. Warnings disappear just when I uninstall AVAST.

I was wondering if it is possible to step back to a previous version...

BTW, my operational sistem is Windows XP (don't know if this is a relevant information but anyway...).

EDIT: Sorry, I did not see your edited post 

Thank You very much for your attention!

[Oscarito]

Back to business!

I've tried to download my previous AVAST version from FileHippo but the installer redirects me to this ultimate version!!! Without a question... 
Any suggestion?

EDIT:    Please... 

[FlyingRobot]

This subject rings a bell.  There was at least one thread some time ago where someone was encountering such a message and it was due to avast.  IIRC, it would only occur if WebRep was installed/enabled and it was thought that was probably due to the browser detecting content that it did not retrieve via HTTPS.  That "non-HTTPS content" being WebRep content injected into HTTPS search results pages.  So that is one thing the OP might want to look into... testing without WebRep.  I'm not clear on whether the avast anti-phishing thing is a yet another add-on, but if necessary I'd test without ALL avast add-ons and see what can be learned.

If necessary or desired: http://www.oldapps.com/avast_antivirus.php.  I know some people who have pulled perfectly clean apps from there without any problems, but I don't use it or vouch for it.