Hi,
I think it was a big problem.I will help you when you try to access the File Open dialog box in the 2007 Microsoft Office system or in Microsoft Office 2010, the operation may not work. This issue occurs on a Windows 7-based computer. When you encounter this issue in Office Word or in Office Excel, you do not receive an error message. However, in Office PowerPoint, you receive the following error message:
An error occurred while opening the file dialog. Please save your presentations, exit, and then restart PowerPoint.
And the other way to resolve such problem is below:

1. Click Start, right-click Computer, click Properties, and then click advanced system settings.
2. On the Advanced tab, click Environment Variables.
3. Locate and select the __COMPAT_LAYER variable, and then click Edit.
4. Set the value of the __COMPAT_LAYER variable to Enable Themes. Or, delete the __COMPAT_LAYER variable.

Thanks, I think it will help you......