General problems with Gallery snapshots not being taken - no items listed in the ULS log
For most problems with the Gallery snapshot problem, there are entries in the ULS - but sometimes there are no items or if there are, there is just the "Timeout Exception". Under these circumstances there is so little to go on that it is hard to figure out how to even get started. Here are some of the general 'how to get started' recommendations that I have:
* First and most importantly, the rendering engine for the entry must be running.
- o For workbooks, Excel Services must be running. The way that snapshots are taken is that a web browser is brought up by the GetSnapshot.exe process and inserted into the document library as a collection of images (representing the worksheets in the workbook).