Leopard Stucks after opening program

[Epke]

Hi,

 

Ive a weird problem! Leopard boots succesfully if I do nothing nothing happens it just works but if I open Safari or Firefox (it looks like it works) I can open sites but after 15 secs whole MAC stucks/hangs

 

Is someone familiar with it? Or recognize it? And can tell me how to fix it

 

AMD X2 6000+

Nforce5 motherboard

8600GTS

 

Thanks