Vista Startup Problems

I have been getting many different error messages when i start up my computer lately. My computer is only a year old and has been working fine on Vista Ultimate until about a week ago.

First, my McAfee Firewall service failed. This happened as soon as I logged into my account on my computer. I didn't know how to fix that problem despite hours of scouring the web and talking with unhelpful technicians, so ultimately I uninstalled McAfee and instead installed Avast.

This worked for a day until I got a Generic Host Exception error. "The Host Service for Windows Processes has stopped working." I read somewhere online that this is usually caused by a program that is incompatible with Vista. The only new software that I had installed was Avast, so I uninstalled that and decided to stick with the Vista security software and my router's firewall.

That worked for two days. Now, I am getting an error that says "Remote Access Connection Manager has stopped working."

I have also noticed that with the last two errors (the generic host exception and the remote access one) the Vista Aero scheme fails and it reverts back to the classic style. The glass effect on windows still works however, which is really weird, cause all the buttons and the inside of windows are all old style. The event name for the last two errors is BEX. I have no idea what this stands for, or what it means.
Does anybody know how to fix this problem?
I am listing the problem signature for the latest error below in case you need it.
Problem signature:
Problem Event Name: BEX
Application Name: svchost.exe_RasMan
Application Version: 6.0.6001.18000
Application Timestamp: 47918b89
Fault Module Name: rastapi.dll_unloaded
Fault Module Version: 0.0.0.0
Fault Module Timestamp: 4791a760
Exception Offset: 6a6760b3
Exception Code: c0000005
Exception Data: 00000008
OS Version: 6.0.6001.2.1.0.256.1
Locale ID: 1033
Additional Information 1: b2be
Additional Information 2: 82109204b3973566ace818217390e302
Additional Information 3: efc3
Additional Information 4: bdb39985db888da86c189f9d4c112241