You may receive "Unreadable Content" when opening files from within Excel 2007, if you have a shellstreams.dll file

by Andrei Dikai

During November 2012, it has come to our attention that an increasing amount of customers have problems with unexplainable "Unreadable Content" error messages when opening files from within Excel 2007:
"Excel found unreadable content in <filename.xslx>. Do you want to recover the contents of this workbook? If you trust the source of this workbook, click Yes."

If you think you are affected by the problem mentioned above, you can test searching your computer for the following .DLL:
C:\Program Files\Common Files\Apple\Internet Services\ShellStreams.dll
C:\Program Files(x86)\Common Files\Apple\Internet Services\ShellStreams.dll
For our most affected customers, renaming this particular .dll file, or uninstalling the application that put it there, has been a workaround to this problem. (If you find a ShellStreams64.dll instead, most likely it will not help renaming it and you need to check the other folder instead.)

If you do not have this ShellStreams.dll, and if all the below facts don't apply, the problem that you have encountered is not the same as the one described in this blog post, and most likely has another cause.

Here are the facts we have gathered about this particular problem:
1. The files showing the problem can normally be opened on colleagues' machines, suggesting that the files are not actually damaged.
2. It seems that these problems usually do not occur when attempting to double-click files from inside Windows Explorer. The scenario that we have encountered was when attempting to open files from within the Excel application, using File - Open.
3. It seems that the files with the problem are usually in .XLSX formats. If you save as .XLS instead, you will not have the problem.
4. Repairing Windows or Excel, or starting Windows or Excel in Safe Mode, does not prevent the issue
5. This has been seen regardless of where the files have been stored, e.g. local drive or network location. But it seems to happen mostly with older files, and not newly created ones.
6. It seems that this only happens with Excel 2007. Excel 2010 or Excel 2013 don't have this problem.

As mentioned above, if you do not have this shellstreams.DLL on your computer, and if all the above facts don't apply, the problem has another cause.