I recently worked on an issue where the customer was getting this error message when attempting to export items from his Calendar to a PST: “The add-in ‘<DLL Path>’ could not be installed or loaded. This problem may be resolved by using Detect and Repair on the Help menu.” We were able to narrow the problem down to a specific set of items along with an Exchange Client Extension (ECE). After debugging it I realized that Outlook was attempting to create a menu for each item it copied to the PST. When a large number of items were copied this design decision causes Outlook to exhaust the memory in the Desktop Heap. Turns out this is a known issue with ECE’s. Unfortunately there is no workaround short of copying less items, or disabling the ECE. As a side note we are encouraging customers to move their ECE code to Outlook COM Addins for Outlook 2007 and beyond. If you are an ECE developer and you have a reason why you can’t move to COM Addins, please let your voice be heard. Apparently Duet has run into this problem as well.