Hello and Welcome, first of all a quick bit of info about the forum and some advice
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I'd recommend reading the forum rules (
http://www.ipadforums.net/forum-rules-help-info/2119-forum-rules-everybody-please-read.html) and looking at some of the stickied threads on here. Many of them are very useful, if you have time (and you'll need quite a bit) I'd also recommend reading the tips and tricks thread (search for it using the search bar) as that has some really useful pointers in it. A friendly reminder about any questions you may have, it's always best to search function to find something out first as the chances are your query has been answered before, whats more you'll often get a faster answer as it can take a while for someone to come along that can help sometimes. If however, you search to no avail, go ahead and post something (preferably in the correct section [speeds up your answer and makes less work for the admins]), chances are someone will be able to help.
As for your question, I don't completely understand quite what you mean but a work around that I can think of that may help you would be to access iTunes on your computer and download the series this way. If this doesn't work come back and let us know. Also, are you still able to download apps etc, and more importantly have you tried downloading other series'? If these work it might be something wrong apples end, if they don't we're probably looking at a problem your end.
Sorry I can't be more helpful.
Sent via iPF from my iPad2 iOS 5.1.