hi, my two cents too!
you should know this is not a legal advice. i am merely forwarding what i have seen and heard as a silent observer during my stay here. you should hire a legal rep right away.

if they hand you a letter like you said, then it is likely you knowingly or unknowingly mentioned somewhere in your statement or implied in the interview that you provided some kind of material support to some political parties, especially maobadis and khaobaadis. such a scenario triggers the patriot act which requires high level clearance for such cases. it might take years to come to this decision. until recent past, the only way forward was to stay in limbo (u can't call that forward, can u?).

i read in some online news site that nepali congress too is categorized under this category as it had taken up arms way back in the past it seems. so any affiliates who worked with nc also are affected. there have been cases where the applicant falls under a case of material support but have no convincing proof or statement to point out genuine fear of persecution. such cases are likely diverted to the immigration judge.

its a complex web of regulations u live in. hire a lawyer paat!