What are the main reasons companies experience failure in the Enterprise Resource Planning systems?

Answer 1

Because they try to customize too much. They will buy a perfectly good system and try to set it up to duplicate their old system. If, instead, they would implement it pretty much as is and change they internal systems to match, it would significantly reduce the implementation cost, time, and risk of implementation. I'm running a very large implementation now, and the customer has insisted on massive customizations. Big mistake.