Internet connect crashing

I have an emac and am using dialup internet, but i often have it set on Automatically connect so when i am away my download can continue(my isp disconnects me after 5 hours) but lately whenever i come back to my computer the connection has crashed and i can't disconnect/reconnect or even shut down the computer or run any programs but i am move the mouse and when i put it over the modem icon at the top it does that spinning wheel icon, i end up having to hold down the power button until the comp turns off then once turn back on everything works fine again. It doesn't do this everytime just every third or so time.

Other than this little problem i am very happy with my mac
help would be appreciated
Thanks :black: