Charts have gone portrait

I'm glad this question is here, because I searched on this topic and only found two mentions of this issue, with no resolutions. I have a customer that has this happen to his charts. Environment is Office 2010, Windows-7, in a virtual (VDI) environment. When he has a workbook opened with charts in it, and the VDI session times out, and he logs back on, the charts (on chart sheets) change from landscape to portrait orientation. This is not a screen-rendering issue, the actual Page Layout option is changed. Here's the funny part. If he closes and reopens the workbook, they switch back to the (correct) landscape orientation. This is most puzzling. At least I know someone else has encountered this issue.
As long as his work is saved, he can just close and reopen. The only issue is that sometimes it will not let him change the orientation, and if there is unsaved work, that will be lost. I will provide him with a macro to change page orientation on chart pages, but that does not address the mysterious underlying condition that causes the page orientation to change.