File examples:
C:\Program Files\Lavasoft.…arrow1.bmp
C:\Program Files\Lavasoft.…bck1.bmp
C:\Documents and Setting All Users\Application Data.… \bob@served by.advertising[1].txt
C:\Documents and Setting All Users\Application Data\Spoybot - Search & Destroy.…\sbRecovery.ini
C:Program Files\Norton SystemWorks\Norton CleanSweep\clnsweep.cfg\123.EXE
Many programs (usually security based ones) password protect their files for legitimate reasons such as AdAware and Spybot Search & Destroy, there are others (and avast doesn’t know the password or have any way of using it even if it did know it).
When you run scans with the above programs and you delete harmful entries that they detect, a copy is kept (in quarantine/restore/backup) in case you need to reverse what you did. These are usually password protected, you should do some housekeeping and delete old backup/recovery/quarantine entries (older than two weeks or so), this will reduce the numbers of files that can’t be scanned.
By examining 1) the reason given by avast! for not being able to scan the files, 2) the location of the files, you can get an idea of what program they relate to.
Files that can’t be scanned are just that, not an indication they are suspicious/infected, just unable to be scanned.
These are legit files.
Two first ones are part of Lavasoft Ad-aware skins.
Third, Spybot recovery (backup) database.
Fourth, the CleansSweep Uninstall database.
Just add them to the exclusion list. 
No real need to add to exclusions list as they will still be listed in the results.
Do the housekeeping and get rid of old backup/restore data from AdAware and Spybot as suggested.
With Lavasoft skins you’ll get a huge list of .bmp files, if my memory not fails me, but after the skin file is added to exclusion list you’ll get only one file results list, were will be show “not scanned due to exclusion” I think it’s better that get several files in the results list every time.
For me too 8)