Sounds like a bit of air stuck in the frontal sinus cavities.
Probably worth a check out with the quack to rule anything obvious out, but it does sound like your symptoms are related to pressure changes. (Ever seen them bread roll wrappers blow up at altitude-simillar effect in the tubes running through your skull.)
Probably worth an ent consult and maybe a scan, especially considering the nature of your job.
Last edited by gingernut; 24th Jan 2008 at 13:16.