Traps leads to a list of likely problems with an ERP system:

• The cost is likely to be underestimated
• The time and effort to implement is likely to be underestimated
• The resourcing from both the Business and IT is likely to be higher than anticipated
• The level of outside expertise required will be higher than anticipated 
• The changes required to Business Processes will be higher than expected.
• Scope control will be more difficult than expected
• Most important of all, and the single biggest failure point for ERP implementations, is the need for change management. The need for change management is not likely to be recognized until it is too late. The changes required to corporate culture are likely to be grossly underestimated.  It is going to be hard enough to cope with the technical issues without having to address major people issues as well