(Urgenttt) Digitally Signing sharepoint Forms using Managed Code in C# _ Signature not valid

Hi,

I have probleme with sharepoint project in vs 2010. I try to sign an infopath form from my sharepoint project (with c#) but when opening my signed form I've got a message box that says : "one or more digitall signature can't be verifiyed in this form, to modify your document delete existant signature".  We are using "Working with signed Infopath forms in Biztalk" to create and verify the signature. It work fine with a asp.net application and the resulting infopath signature are valid. infopath do recognize this signature and they are valid. But when we implement the same methode in sharepoint project and sign the same infopath form the resulting signature are not valid.

Thanks