simpleminded but balky migration to macbook

I have been trying to migrate info (programs, files, music, etc) from my iMac (currently on Tiger) to my new macbook.

I hope to also migrate info from my powerbook G4 (recently upgraded to Leopard from Panther). The powerbook immediately developed a problem and is now in the shop. I have all the info backed up on a La Cie hard drive, but that doesn't have migration assistant. Also, just in terms of transferring info, I don't have the right kind of USB cable, so I can't even connect the La Cie to the macbook until I get a new cable.

That leaves me with the iMac. Nothing I try works. I get as far as plugging in the Migration Assistant numbers and having the computers seem to recognize each other, but then I keep getting an error message about the connection. They are both on the same wireless system.

I also tried with an ethernet connection, but because all I know to do is hook the computers together, they don't seem to know that the other is there (based on the finder window).

I also tried to move my most important program to iDisk so I could just transfer things that way, but then I get the message that not everything can be copied.

Can anyone offer a few practical suggestions for someone who buys Macs because she doesn't know how to deal with these things? Any help would be appreciated.

-Karen