Why is this scan taking

[midnight]

so long?  It has been stuck at 93% for at least 30 minutes.

[Charyb-0]

Sometimes when scanners get stuck they need lubrication. Have you tried using scanner grease?

[polonus]

Hi -midnight,

To get back on-topic and jokes apart. Did you hold the scan up and then tried to continue? This sometimes may help.
It could also be that the scanner has struck a corrupted file or tries to get to one who has left an earlier path.

A wonderful small tool to launch and see what has brought the scan to a standstill is "My event viewer". Get it here: http://www.nirsoft.net/utils/my_event_viewer.html   
Nir Sofer is a wonderful Israeli software developer of special tools for the Windows OS, it is a splendid and simple tool,
launch it wait for it to finish the scanning and look for the time and Windows event that halted the Avast scan.

greets,

polonus

[Pondus]

Sometimes when scanners get stuck they need lubrication. Have you tried using scanner grease?

exactly .... HP printer scanner grease        
http://www.alibaba.com/product-detail/fuser-film-sleeve-grease-for-hp_921945967.html

[polonus]

Hi friend Pondus, reading the "greasy" parts now: https://community.spiceworks.com/topic/227857-avast-boot-scan-stuck-black-screen  That was a give away as our -midnight attached an image. And MBAM had such problems also.
Somehow -midnight got the scanner get stuck on aswRvrt.sys. Check that is not corrupted. It may hang on C:\Windows\System32\Drivers\aswrvrt.sys until the computer reboots. So rebooting the computer may help.
In case it is persistent creating a bootable USB drive may do the trick. If poor -midnight is very unlucky it may be the first sign of a dead hard-drive or she should get a second opinion of a hardware specialist here. If so this may help to recover: http://www.krollontrack.com/data-recovery/

polonus

[Charyb-0]

Hi friend Pondus, reading the "greasy" parts now: https://community.spiceworks.com/topic/227857-avast-boot-scan-stuck-black-screen  That was a give away as our -midnight attached an image. And MBAM had such problems also.Somehow -midnight got the scanner get stuck on aswRvrt.sys. Check that is not corrupted. It may hang on C:\Windows\System32\Drivers\aswrvrt.sys until the computer reboots. So rebooting the computer may help. In case it is persistent creating a bootable USB drive may do the trick. If poor -midnight is very unlucky it may be the first sign of a dead hard-drive or she should get a second opinion of a hardware specialist here. If so this may help to recover: http://www.krollontrack.com/data-recovery/polonus

Polonus, it appears that she was running a quick scan and not a boot time scan. I'm wondering if the scan completed and wonder if it is a GUI glitch and if it is repeatable. I have had scans behave like this which, at times, were unexplainable. Processor and/or disk busy? I would check this if it happens again.

[polonus]

Hi Charyb,

Then I am glad for her it wasn't a boottime scan. With -midnight a junk removal routine always works miracles. A proposed JRT scan has saved her on many occasions. I do not know why crap enters her machine that easily, but it is a fact. But as she is learning all the time, her situation is going to improve also over the long run, and others may profit from the acquired insights as well. 
If what you say holds true, I would like to hear what free mem she has got left. You need some more that 10% else your comp is so fenced in "the horses cannot leave the corral and starts to bump." 

pol

[midnight]

Hi polonus,

This is how much free space I have.

[midnight]

I run another quick scan last evening and it took around 15 minutes to complete.

[polonus]

Well then this was a glitch then. It happens...

pol