Might be a bug then,
What game version are you running? (You can see it in the main game menu, in the lower left hand corner)
If you aren't running the latest version, then I suggest you update your game and see if that fixes this issue.
You can get the patches here:
http://www.shipsim.com/downloads/patches.php
If you have V1.0, then download and install the V1.0 to V1.3 patch.
If you have V1.1, then download and install the V1.1 to V1.3 patch.
But if you allready have V1.3, then forget I said anything.
Regards,
Fred