We seem to have the same problem as my problem occurred exactly as I unlocked my 6th character by leveling 50 my 3rd.
And as with you, I was just so desperate to play the game that I too went ahead and replaced my 3 level 50 characters. I too did the shuffling about the characters ( Like scout, scout, engi, engi, rifle, rifle or rifle-engi-scout-rifle-engi-scout all sorts of order combination hoping this would fix it) to no avail. Still stuck in a loading screen. Sigh, now I feel like a total idiot for replacing my 3 level 50's. So much time put in those classes. I went through all that BS lag and often times lonewolfing it when my friends weren't playing just to get those 50's and now they're gone. God I do love this game but Ubi is making it so easy for me to hate them.
I noticed one thing amidst my shuffling of characters... it seems there is one specific slot that has the mk14 and m60 usable for unlock. Its the 3rd character slot. If I put a rifleman character in any other slot be it 1st, 2nd, 4th, 6th or 5th, the mk14 is not visible and the m60 is locked. It is only when I "replace" the 3rd slot where the original rifleman default slot is that the m14 and m60 and their respective bodark counterparts are unlocked and usable.
This only happens under my profile. I can use my nephews profile and go into a multiplayer game every time. I do also have 2 level 50 characters, but for some reason have all 6 characters unlocked. According to xbox I need to contact Ubi on Monday.
This happened to me as well, you might not have noticed your levels dropped randomly, usually if you play one match your original levels come back. So for ex I had a 50 scout, level 4 scout etc, my level 50 dropped down a couple levels and I played a match and I got my 50 back with also another Scout class, because they game thinks you just hit 50 again. Also if you unlocked anything on Ghost Recon Commander and equipped it online it can cause the loading problem. I tried removing the unlocks from my character, switching my character before the game ( all options Ubisofts support gave me) until they retired my ticket for absolute no reason.. Luckily I have Halo 3, and Battlefield to play. I was extremely eager to try resetting my characters but this game is so unreliable I didn't think it was worth it, along with level drops, and disconnects, and now tons of players can't load into matches at all. If it makes you feel any better I'm in a top squad (Affiliated) and I haven't been able to play in 3 weeks due to this problem. It's seriously out of hand.. ;(
well it definitely is because i maxed my 3 characters and unlocked my 3 extras i just played 5 games in a row with surprisingly no issues under my sons screen name none of his characters
are past level 15 he doesn't really play cause all the lag is BS and theres to many campers funny considering he only 7yrs old.
then tried to play under my name and got the infinite loading sceen
Sorry to say this, but let your son play Call of Duty, its way easier, it doesn't require an intelligence quotient above 1, and if you truly loved your son, buy him Lego games