This is more annoying than a problem but here goes. I have a USB modem that I use for high speed DSL. I've had it for ages as my old PC didn't have Ethernet connections. For some reason it's always popped up the dial up dialog when I first connect to the internet. I then have to wait about the same amount of time that you would wait if you were using a dial up modem. Does anyone know why this is happening? Once I connect I'm fine but it's a bit of a pain if I want to start up my PC and jump on quick to check something.

It's possible you have a PPPoE connection. PPPoE is a something that uses dial-up style connections over Ethernet (and USB in this case).
You can read more about it at http://en.wikipedia.org/wiki/PPPoE
It basicly gives the Internet Provider more features with the connection. Like as that artice says "user authentication, per-user service/control, usage metering, billing, etc."
When I had DSL I didn't have it but I've read some Internet Providers do.
If they require PPPoE to be used then you need that connection to use the service.
If you don't like it you will have to talk to your Internet Provider about it.