Browser Problems

I am having occasional trouble with Firefox (my default browser) as well as IE .
Sometimes, not every time, when i start firefox, i get a popup that says the following :
You have Chosen to open
(logo) firefox
Which is a: application/ octet-stream
from: http://www.google.com

>What should firefox do with this file ?
- Open With (browse)
- Save File

My homepage is not http://www.google.com , my homepage is :
http://www.google.com/firefox?client=firefox-a&rls=org.mozilla:en-US:official

I will close that window with the "X" .
Other times, I will attempt to open Firefox, and it never opens on my screen, even though it DOES show up in Task Manager - Processes list .
When this occurs, I attempt to "end process" and firefox either will not close, or takes a very long time to close. When this happens, IE will not work, either, having the same symptoms as Firefox.
I have totally removed all files of firefox, and re-installed, yet the problem continues .
As I am not certain at this point that this is a malware problem, I thought I would post in the software forum first.
I have run Malware bytes, SAS and Avira, none of which find any malware, and i use CCLeaner daily .
If this sounds like a malware problem, I will complete the READ and RUN ME FIRST section .
Thanks for your time !

 

Don't just look for Firefox. Also scout out anything that says Mozilla.

 

Right. That's what i meant, I got rid of everything associated with firefox, which would include mozilla, since firefox is the only mozilla product i use - or do you mean processes entries in task manager ?
Should I just do the READ and RUN me FIRST ?

 

The only add-on I have is Adblocker Plus, and i use Avira anti virus .

 

So I continue to have this problem with Firefox locking up on me, only showing itself in task manager "processes", from which I am unable to "end process" and have to restart the computer to use any browser at all .
I am beginning to think this is a virus, though I have run newly updated Malware Bytes, SAS, Avira, and Spybot all in safe mode, everything comes up clean.
If nobody has any input within a couple of days, I will just move on to the READ and RUN me FIRST section .
thanks.