Cannot take any action after ending scan

[system]

I have just installed the last version o Avast Free Antivirus, scanned my PC and got seven alerts about msmpeng.exe.
1.- I can see this is Windows Defender so, is it a real infection or just a false positive?
2.- When I go to the results page where I am supposed to be able to take some actions on these results, I cannot take any.
I cannot choose any result so I cannot take any action on it. I guess there should be any place to mark the desired result and then choose the action but there is no place like that.

Could any of you, please, help me?

Thank you.

[system]

What is your operating system and Service Pack level?

It it 32-bit or 64-bit?

What is the actuall location of the detected msmpeng.exe?

Get the latest Windows Defender updates from its portal:
http://www.microsoft.com/security/portal/Definitions/ADL.aspx

[system]

My OS is WinXP SP3 32bits
“msmpeng.exe” is located at “C:\Archivos de programa\Windows Defender” (that’s spanish, it must be “C:\Program Flies\Windows Defender” in english).

[system]

http://forum.avast.com/index.php?topic=55820.msg472994#msg472994

@DavidR post:3

The reason for the error is you can’t move a memory location to the chest.

It also looks like you have been tweaking your scan settings not knowing the impact that that tweak might have. This issue normally comes about when you check the Ignore virus targeting option in the file system shield, sensitivity section.

[system]

Thank you but I think that’s not the issue as I have checked the system sensivity section in both scans I made (getting the same results) and none of them has the “Ignore virus targeting” option check (see attached images).
In fact, that’s not issue for I still haven’t get the point to have an “access denied” error message 'cause the real issue is that I cannot take any action, I cannot select any result to select the action to take with… of course, I cannot even click the Apply button as no result has been checked and no action has been selected.