I've had this problem recently with inserting files in Outlook, or opening / saving files in WORD.
PROBLEM: I am using Windows 7 (and sometimes Windows 8.1 at home) with MS Office products. I open a file dialog to perform a file operation from within Word, Excel or Outlook. As soon as I click on a network drive or folder from the navigation pane on the left side bar of the file dialog, the application hangs and there is no content in the file dialog. Waiting does not resolve the issue.
SOLUTION / WORKAROUND: Open My Computer, This PC, Explorer or whatever MS calls file explorer today. click the same network folder / drive as the one that caused the Office application to hang.
In my experience, the network folder location opens in Explorer immediately with the Office application file dialog suddenly becoming responsive.
I only discovered this because when it first happened recently, I got tired of waiting for Outlook to sort it out. I opened Explorer to check to see if the network shortcut was dodgy and the simple operation of clicking on the netowrk location in Explorer resolved the issue.
PS, thought I'd post this my first post to Superuser.com in appreciation of all the free advice I've received over the years from this great site. Its sooooo much easier finding solutions to my windows problems than my Iphone problems - Windows issue - google it and find great sites like this with posts from people who CAN help. Iphone issue - google it and spend weeks trawling through forums with people offering inane advice or telling you that you shouldn't expect iphone to handle feature "x, y, z" or that they should just put up with some stupid workaround.
PPS - my "solution" is not a solution - its just a stupid workaround - at least it works (at least for me!)