problems with internet connection

[callosa]

Hello - I have installed avast! (latest free version) however, immediaely following installation I am unable to connect at all to the internet.   I have had to use system restore in order to connect but then of course it deleted avast!   This has happened about three times in the last 24 hours.  Any advice would be appreciated.  By the way I use Vista and Internet Explorer or Firefox.  I have been unable to get Firefox back at all....

[SafeSurf]

Welcome to the forum callosa.

1.   What is your OS?  Updated?
2.   What other security software do you currently have or did you have in the past on this machine including:
- Antivirus (AV)
- Firewall (FW)
- Trial versions of AV, FW and other security programs
- Other security software

- If they were in the past, how did you remove them (the vendor's uninstaller's tool or  another way)?