Help Desire loses mobile connection when launching Nav progs

[androidloop]

Hi I am using HTC Desire with Android 2.1 update 1, i had never had any problems with mobile internet, however every time i launch any type of program like "My tracks", or "Maps", the second the program launches and the GPS icon shows up on the upper panel and fixes on a satellite, the mobile network icon disappear and the phone can not connect to the mobile internet until i turn it off and turn it on again. this is systematically and happens every time no matter what i try. any help please ??? i can use any GPS program because of it....