If your having that much trouble scanning for channels then you might be suffering a signal problem.
Allot of people have had this problem in the dbox forum. The signal could be to weak, to strong or contains a high error count.
The signal I receive from the cable company is to strong and I have to use a filter, its so strong without the filter I get an electric shock off the cable when plugging it into my dreambox.
First of all check the cable you are running to your dreambox and make sure its not damaged or twisted badly, if so replace the cable. Next try a signal booster, Arg*s sell one for around £10 and if it doesn't help they will take it back within 14 days no questions asked.
If amping the signal makes it worse then try buying a filter on fleebay. I don't know the correct name for it but I'm sure if you search you'll find one. Mine needs a 12db filter which is the highest you can get (I think).
Trooperboy