It could be one of two problems .......
Does it only happen when using MP or during single play also?
Does it happen with both default and addon aircraft?
If it is in MP and single play then it's probably the addon aircraft or one of it's gauges causing the problem.
If it is only in MP then.....
It could be a port problem..... are you on broadband or cable through a router?
Do you have a firewall running?
If so then you need to make sure that the correct ports are open to allow the sim to connect ..... likewise with the firewall.
Are you using Gamespy to connect? ...... if so then check any help pages there.
If you are using FShost .... or just connecting via IP .... then you need the module that allows you to connect from
www.chocolatesoftware.com .