This is a stumper for me. 
HP Pavilion h8-1010 Desktop Win 7 x64 - SP1
Came in for cleanup/malware removal. Had minor infections, normal toolbar stuff that we see, such as ask, etc. I am certain that the system is clean, ran tweaking tool after cleanup. Installed Bitdefender 2015 AV.
The issue is that the File download setting keeps getting toggled to "disabled" by something and we end up with
"Your current security settings do not allow this file to be downloaded".
I can do the following steps, and all is well for about a day or so, and then we end up with the same issue.
I've reset the browser, disabled the AV in case Bitdefender is doing something quirky but it still occurs.
I haven't been able to spend a lot of time on it today, but I thought maybe I would create a new user profile and see if it occurs there. Customer does not want to use Firefox as a workaround, so I haven't even tried that.
Any ideas at all?

HP Pavilion h8-1010 Desktop Win 7 x64 - SP1
Came in for cleanup/malware removal. Had minor infections, normal toolbar stuff that we see, such as ask, etc. I am certain that the system is clean, ran tweaking tool after cleanup. Installed Bitdefender 2015 AV.
The issue is that the File download setting keeps getting toggled to "disabled" by something and we end up with
"Your current security settings do not allow this file to be downloaded".
I can do the following steps, and all is well for about a day or so, and then we end up with the same issue.
Internet Explorer.
Tools » Options.
Click on the Security tab.
Select the Internet Zone.
Click on the Custom Level button and then scroll down to Downloads.
Make sure to set File download to Enable.
Click OK.
I've reset the browser, disabled the AV in case Bitdefender is doing something quirky but it still occurs.
I haven't been able to spend a lot of time on it today, but I thought maybe I would create a new user profile and see if it occurs there. Customer does not want to use Firefox as a workaround, so I haven't even tried that.
Any ideas at all?