Summary:
Pivot reports aren't designed to run on a 64-bit Internet Explorer. This is due to a limitation within the Office XP Web Component (OWC) that creates a framework inside a browser to allow Microsoft Excel to run and execute, within the web browser itself, without the need for a full fledged Microsoft Office Suite. In fact, the use of OWC is suppose to require the user to have Microsoft Office and in particular Microsoft Excel installed and licensed on their machine but, the OWC itself doesn't force it. Note that the Microsoft Office XP web component is an old ActiveX plug-in, specially designed to work only with Internet Explorer and not any other browsers like Firefox or Chrome. Also, it could only interpret 32-bit code and not 64-bit code hence, it wouldn't work with a 64-bit Internet Explorer.

Recommendation:
It is recommend to export the Web TimeSheet report data to Microsoft Excel and all the functionality that is done within the pivot reports of the Web TimeSheet application, can also be effectively manipulated within any modern spreadsheets like Microsoft Excel. This helps us create the pivot on our own and according to our needs.

Note:
Since Microsoft has stopped support for Web Components since the release of Microsoft Office 2007, there is no improvement or enhancement done for the Pivot Reports reporting functions in Web TimeSheet. Pivot Reports in Web TimeSheet now exists only as an additional feature and we haven't yet dropped the functionality, purely because customers really wanting them.