broken header returns 404 when link to page is correct? (Joomla CMS)

[SchweppesAle]

hi, i've recently migrated our site over to Joomla 1.5; everything looked like it was running smoothly until our google webmaster tool reported about 1450 broken (404) links.  We currently only have about 1280 indexed so I did some digging and found that the headers are somehow broken.  Here's an example someone from another form pointed out to me -->

 

 

http://oyoy.eu/page/headers/?full=1&url=http://www.nptechnews.com/content/view/130/60/

 

as you can see from the link; the page will pull up correctly however the header is returning a 404 error.  How would I go about correcting this before our pages are de-indexed?  Thanks in advance for your help, I'm seriously at a loss with how to correctly handle this.

 

edit:

thought that it was also important that I mention the backlinks plugin has been enabled and at least (appears?) to be functioning correctly