Welcome to the boat mate
I see that you haven't downloaded any mods so you might be playing stock.
To really get the game to play right you must add some of the mods found here
http://www.subsim.com/radioroom/showthread.php?t=155786
and be playing the V1.5 version of the game, all the new mods ore for V1.5 or the U Boat missions add on. There are just too many issues with stock.
Magic