Right click scan not detecting

If I were to have an infected file, and were to scan it using the right click menu option and perform a scan, nothing would appear as a threat. Yet if I open the main program and scan using the folder scan option it will find it. Could someone explain to me how this works? I have gone through all settings that I can clearly see in the program and set for High heuristics, PUP, all files and extension, and all packers.

My info:
Avast FREE!
Program Version: 6.0.1000
Virus Definitions: 110409-1

What exactly is detected - when it is detected? (full malware name, full location)

Response:
Results of the folder scan using main program:
resultbar-setup.exe|>$0\uninstall.exe as PUP:Win32:Zwangi-V
resultbar-setup.exe|>$0\resultbar.exe as PUP:Win32:Zwangi-J
resultbar-setup.exe as PUP:Win32:Zwangi-V
Location: Documents and settings\Username\My Documents[testing folder]


For some reason Avast! right click on scan does not detect as many as a folder scan or real time shield as in this cause it does not detect anything. Could one change the settings for right click scan somewhere?
Is there a reason or solution to this mystery of mine?

My Info
Windows XP SP3
Avast FREE!
Program Version 6.0.1000
Virus Definitions: 110409-1

Right click scan on Demand not detecting what File system Shield does.

I have submitted several viruses of different forms to the lab along with a txt file explaining what is going on.

Simply put, Right click for a scan on a drive, folder, or file is not being detected.
However if I use the main screen option to scan a drive, folder, or a file from there with custom settings it detects the viruses. This is a problem that I would really like to solve. I know not everything can be fixed but this makes the scan on demand option pointless for avast in my environment.

Could someone shed some light on this please? ???