I have the same problem.

I have the same problem since 24-2-12.

iam useing google crome now, loading problem went away, also i got rid of all the junk(decorations, signs and old buildings from old missions you can store all of the above) and i leave a few spaces between everything

I have been able to get in to my game but atleast 5 or 6 times a day I get locked out. Usually for 15 minutes at a time, but it has been as long as a few hours. Any time I refresh the game it happens including each time I have had to contact support and they asked me to refresh..This time around I get stuck on the loading screen but there are a lot of other times I load to a blank green screen. Its getting very frustrating and contacting support always leads to the same response "they are working on it". :(