Hello asdfssdff,
Welcome to MSDN forums!
I'm going to help you to trouble shoot the problem. In normal case a customization which was built in VSTO 2005 SE will run in Office 2007 environment without any problem.
Please note following things:
Please make sure you have Office PIAs installed in your client machine.
Please make sure you have grant full trust to the assembly, in order to get permission to run it.
Most possible thing is you have some errors in your startup method, so one thing you could try is comment all the code in startup method and run it again.
Hope this helps you, looking forward to your feedback.Thanks.
Tim Li
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