The same thing occured to me some time ago. All internet browsers crashed whenever a link between browser and file explorer was made, downloading or uploading a file. Next I noticed it affected MS Word too. Saving existing document worked fine, but Word crashed when trying to save it as a new file (file explorer opens).
I tried sfc /scannow several times with CMD opened as adminstrator and it always stopped at 27%. I can't remember the error, it was something like "could not execute" or something. I am using Finnish version of Win7 so sorry for bad translation.
After that I tried sfc /verifyonly (as per www.sevenforums.com). There was no problem with that, but even after that /scannow stops at 27%. Then I tried (at cmd again) Dism /Online /Cleanup-Image /RestoreHealth (as per forum.thewindowsclub.com). Cmd says there is no such funcion, so i tried same but instead of /restorehealth I used /scanhealth or /checkhealth (can't remember which). This was executed well to the end and after this I can use sfc /scannow and it completes. I did it 3 or 4 times as instructed.
There was also some windows updates involved, and I reinstalled some of basic drivers with acer recovery tool.
After restart, all works again! Even the old problem that I had before was gone. The old prolem was that I could not install a printer or "print" a PDF file because some of the printer services were down and windows was not able to start them. Now printing works also.
Just thought that this would be worth sharing, this is kind of unique problem and there will be people struggling with it in the future.