If you insert a column into an Excel workbook that is bound to TFS, you may get the following error:
TF84034: Team Foundation was unable to initialize the workbook. This document will no longer be associated with a Team Foundation server.
When I first heard about this error, the customer had moved the workbook between machines. I assumed that the workbook had lost it's bindings to the TFS server and it just needed to be rebound using the "tfpt changedocurl" command from the latest Team Foundation Power Tools.
Update the server information. TFS server information is stored as metadata in TFS bound Excel or Project files. But there might be cases where server is renamed, port number is changed, or the protocol is changed (i.e. https instead of http). This command updates the server information on existing files.
Usage: tfpt changedocurl filespec /server:serverurl
However it wasn't this problem. After searching the knowledge base I came up with this article:
After checking some more with the customer, they realised that they had in fact added a column and this hotfix fixed their issue.
In the article it tells you to contact Microsoft Customer Service & Support to obtain the hotfix. However in this case you don't need to, since VSTS advertise their hotfixes and make them public. You can download the KB946458 update from MSDN Code Gallery.