Error when user try to submit infopath 2010 form into sharepoint 2010

Question

Dear Experts,

I created a simple custom list in sharepoint with 1 extra column called "a1". I edited this form in infopath 2010 and published back. However, whenever I try to fill out the form by "Add new Item" >> "Save" I get a Critical Error and it just says Correlation ID : xxxxxxx.

Please help me thanks :)

PS. If i don't edit the form in infopath 2010 I can "Add new Item" fine.