A user has Excel 2010 and is attempting to open an Excel document from our Office 365 Sharepoint server. Excel Crashes when attempting to open the file with a faulting file "mso.dll"


The same file, when dowloaded and opened locally does not cause Excel to crash. Other Excel files from the sharepoint server continue to force it to crash.

Anyone have any ideas as to what the problem may be?


A different user in my org is reporting the same issue. Updates were installed last night for both of these users. Anticipating that may be the issue. Testing now. Updates installed last night were:

KB3093983   Security Update 10/14/2015  NT AUTHORITY\SYSTEM  
KB3097966   Security Update 10/14/2015  NT AUTHORITY\SYSTEM  


Appears to be related to opening a ".xls" or ".xlsx" file from Sharepoint (office 265) in Excel 2010. Might be related to a "trusted sites" issue.

Update 3 - December 4th

Removing the updates listed above no longer seems to fix the issue. Looks like it is a new update or something that is breaking it again.

  • Windows updates don't appear to be the cause, as a third user in our org who can successfully open the file, was able to grab all of the updates from last night, and can still open the file. So far I have tried a repair install of office, and adding the site to the compatibility list in IE 11. Same issue with Chrome and IE11. – user76211 Oct 14 '15 at 22:45
  • Removed update KB3055034, of which there were 3. Issue appears resolved, verifying now. – user76211 Oct 15 '15 at 14:11

We had the same issue, but we are all 2010 - Office and SP. We uninstalled KB3055034 and it solved the issue for us. The update deployed a new mso.dll file. If you check the Event Viewer, you should see this in the application log.


  • 1
    I removed all 3 updates that showed up under KB3055034, and blocked them from installing the the future. After restarting, the problem is resolved. – user76211 Oct 15 '15 at 15:50
  • 1
    Make sure to remove KB3054886 as well. – user76211 Oct 21 '15 at 17:21

We had this problem initially on our windows xp machines, and resolved the issue by uninstalling KB3055034 (which seems to involve mso.dll). I guess the updates hadn't made it to the windows 7 machines yet.

  • Make sure to remove KB3054886 as well. – user76211 Oct 21 '15 at 17:21

Found the bad update. Uninstall all instances of it and hide it from Windows update.


Information about it is here: https://support.microsoft.com/en-us/kb/3101521

This issue occurs because of a known issue that exists in update KB3055034 which is cumulatively included in this security update.


Question: Is the user's machine from where you are attempting to open the Excel files joined to your domain? I have two machines with identical WinUPd installed, both running Windows 7 Enterprise (64bit). Both using Office 2010 (32bit). Both are accessing Sharepoint via the web. My laptop (joined to our corp domain, pass thru auth via the AD/Sharepoint) will open files fine. My desktop at home (manually logging into Sharepoint) will crash Excel when attempting to open files.

One thing I did run into which I haven't been able to narrow down yet though.. If I flatten/reinstall Office2010 and attempt to open the files prior to doing the barrage of Windows Updates, it will open them. This issue has only sprung up it seems within the past couple days.

  • Good looking out. I am about to spin up a vm with our image that was built prior to yesterdays image, and see if that works. – user76211 Oct 15 '15 at 13:45

I had same problem here and the issue was solved by overwriting the new mso.dll from the last MS office 2010 update with an mso.dll that was from before the update.

For me mso.dll version 14.0.7153.5000 was the good one.

  • 2
    Where did you find the old version? Explaining how and where you got that version of the file would make this a better answer. Downloading dll files from the internet can put your computer at risk, so be careful. – Cfinley Oct 15 '15 at 15:11