I managed to extract one of my sites by going to the registrar directly, and the registrar took it away from them and transferred it for me. (Apparently mapname didn't respond to them, either.) ipowerweb is not a registrar so they depend on another registrar; there is a list at:
http://www.icann.org/registrars/accredited-list.html
You can usually look the actual registrar in a whois for the appropriate domain. Yours appears to be ONLINENIC, INC. Contact them and fill out a complaint about ipowerweb. They already know that the site is yours for the next year - the ns record expires Mar 2007. However, this procedure only worked with one of my sites; the other registrars didn't respond. You should be prepared to show that last year you registered the site with ipowerweb since ipowerweb has made itself the contact (that is how mapname held half my sites hostage).
By the way, your dns records point at the nameservers of
http://www.onlinenic.com/dnsdiy/, so you might see if you get back up there, switching them to frame vizaweb, for example, as a stopgap measure until you make the transfer succeed.
The second thing I did was email the company that if they didn't release my sites for transfer, I would start describing my experience online at sites like this one. If you search "mapname.com" you can see the results -- they did nothing for weeks and I pretty much filled out a complaint somewhere once per day. My complaints appear in the about half of the top 20 results of a google search.
I doubt this actually helped because if there was anyone reading their mail at mapname they probably would have just released my sites rather than keep me waiting for weeks, but there is a certain satisfaction is doing your civic duty. If you follow this path, I'd advise breaking your story into pieces: first this happened, then this happened, etc. to make it easier to follow; the current post is something of a jumble because your story, with problems with both a hosting service and a dns service/reseller. Why, for instance, did ipowerweb complain about a chargeback when it was vizaweb that you took the money back from? Are these the same company? But if so, why are you trying to transfer from ipowerweb to vizaweb? Take a deep breath and write out the story chronologically, including when you registered, etc. That will help make the situation understandable.
Good luck. I know this is miserable. Make sure your new registrar has a better reputation.