Just got rid of 2 annoying errors related to PowerPivot feature of Excel and SharePoint 2010.
1. PowerPivot in Excel 2010. When you try to create a PowerPivot table or chart in Excel 2010 you get this error. It my case had nothing to do with the size of the workbook. Very small spreadsheet and still was getting this error: “The command was canceled. Please press F1 to get the help topic ‘Excel Window: PowerPivot Field List’ for more details.”
To solve the problem configure Excel default save format. Go to File / Options / Save and select Excel Workbook (*.xlsx) format.
2. In PowerPivot Gallery thumbnail preview images are not generated. Red X icons are displayed instead. Who would believe that it was old IE7 browser that happened to be installed on SharePoint 2010 server ! Upgrading to IE8 solved the problem. Apparently the GetSnapshot.exe process that generates the preview images uses IE components under the hood.