Can i get help with ADE? I need help with a person to trouble shoot

Thanks! This is quite a long process - I've been working on this since I got the damned kobo at christmas.  I'll start at the beginning. 

My problem started with a defective kobo cord. When i first got the kobo, I tried connecting to my mac (Mac OS X 10.7.5). My mac kept shutting down so I tried the first kobo on my mum's pc. That didn't work but when I borrowed with a different cord I could get the kobo to connect. I downloaded and authorized adobe ADE 4.5 on my mum's computer (perhaps my first mistake). I still couldn't get it to work though - at that point I didn't realize i needed overdrive. Then I returned the initial kobo and got a new one with a functional cord. I've now deauthorized and deinstalled ADE 4.5 on my mum's computer.  I authorized my computer and kobo with ADE 4.5. I also created an overdrive account.  That still didn't work - the error message I had when I tried to open a book was something to  like 'you don't have permission to copy this item'. 

Since then I've tried authorizing and deauthorizing many times with ADE 4.5.

At the suggestion of someone at KOBO I am now using ADE 3.0. At this point I can see the book I want from the library on my kobo file (the book shows up in my finder under kobo as well as in the kobo bookshelf in ADE 3.0). But when I try to open the book in ADE 3.0 i get this error message: Activation server error code E_ADEPT_INTERNAL. and underneath it says: Digital editions encountered an error on the activation server.  THe book doesn't show up on the actual kobo device. 

Thanks for trying to help with this!

Anna