Topic: Closing an AutoViewer window locks up navigation with IE7

I have created a site in which several pages contain one or more link to open an AutoViewer gallery in a new window.
Each gallery is defined in a separate folder.
Everything works fine as long as opening and viewing the galleries is concerned.
The problem is that when I close a gallery window, navigation in the site from the main window becomes impossible with IE7. IE searches for ages the target page before declaring it cannot reach it.
Strange enough, this problem is not systematic, from time to time it does not manifest (or I have not identified the conditions), it does not seem to happen with Firefox and this site used to work some months ago with IE (perhaps in a different version).
When navigation on the site is locked up I can navigate in other websites opened in a new tab but to get IE operating again on my site I have to close it and reopen it.

Any clue on what can cause such a behaviour?