Hi i am having this same error, just recently bought the nokia lumia 800 handset and have never used a windows phone as im normally an android user "and to be honest i have had nothing but bad experiences!!! The error im getting is when i try and install the "Marketplace" it tells me to "Refresh" Marketplace and under neath it says ("Attention required. Press Here") i press where it asks (says Pending "then" Downloading "gets upto 50%" then gives Error code: c101b000 with message saying ( There has been a problem completing your request. Try again later ) Been trying for 2 days now
NOT HAPPY AT ALL!!!