Yesterday I added a page to my dnn site - saved it and then opened it and added a module.  Then I moved to a different page and noticed the page I had just added was missing - not showing in the menu - so I added again and then ended up with 2 pages - neither of which had the module I originally added.  When I added the module again the page then displayed 2 instances of the module.
I deleted all the new pages, emptied the recycle bin and started again only for the same thing to happen again.
Any help or ideas on this would be appreciated.

Thanks Cathal for your response.  I dont think its on a webfarm or garden.  I have another site using DNN on the same host since November 2010 which has never given me such issues.  I did however have these issues with an instance of a different CMS in 2010.  I recall the support for that crowd telling me that my host had to make some change or other involving Application Pool but cannot remember any more than that, just that the issues are so similar.

My host company moved my site into a different app pool and it seems to have helped greatly.  While the problem is not completely gone, it only happens intermittently now.  Thanks for your help.