I receive a lot of questions from customers where they have taken advantage of CRM's Transaction Launcher functionality. What I have noticed most is that while there are lots of documents, articles and guides available that explains step by step configuration, there are hardly any that actually tells you how to debug it. The WIKI page I created actually contains all the steps that I take on a regular basis when debugging a transaction launcher issue.
You can access the WIKI page by clicking on the link below:
SAP CRM Transaction Launcher to SAP ERP BOR Objects - Debugging
Do let me know if this was of any assistance and any if you would like to see anything similar in the future. Enjoy!!!