I upgraded my dnn installation from 4.5.5 to 4.9.0.  The upgrade seemed to go smooth.  I was able to use the different portals and i proceeded up make sure all of the modules were up to date.  I called it a day at that point.  The next day, I noticed an error or two when browsing the site.  I looked into it a little and found my SEO Pack module seemed to cause problems with the blog entry, so I turned off link rewriting. The blog posts were visible at that point, but later that day I noticed the site not working at all.  I restared IIS and the site started working for a while....then, again the site would be too slow to load a page.  Once in a while the page would load and I would click some links for testing and errors would show up...no erros were consistent.  At that point, I cut bait and restored to my pre-upgrade version of the site.  I killed a bit of data since there were some inputs between that period of time, but now the site is up and running.  This is the second time I have upgraded into a failed situation.  I'm getting to the point that upgrading seems very dangerous.  I thought I would post my concern and see if anyone has some suggestion as to where I should start looking for learning resources.  I'd prefer to go into the next upgrade with a little more understanding than I have now.

Thanks for your time.

+Bill