i had this problem with my girl friend a few months ago, we really wanted to have sex but i couldnt maintain an erection, i was hard up till the point of puttin on a condom and then it just dissappeared. i think the problem was i was nervous as hell, id had sex before so it wasnt like this was my first time but i just got really nervous! we got round it eventually, just get him to relax and not get too uptight about things. what really upset me the most is that my gf thought it was her fault, this was most definatly not the case so dont worry about it. hope this helps