We have had our olddomain.com for 9 years and ranked in the top 5 on google for all our keywords. We recently did a switch over to our newdomain.com having a 301 redirect from our olddomain.com, for the first three weeks it retained our rankings for all our keywords but all rankings were still pointing to our olddomain.com but it had our new title tags and content. Now over these three weeks I noticed that some days our newdomain.com would show in place of our olddomain.com for 1 day then it would reset back to the olddomain.com. Now this past weekend we vanished from the rankings, not even listed in the top 2000 pages for any of our keywords, but yet still listed in google if I type both our olddomain.com and newdomain.com. Our Page shows that it gets spidered from google every 3 days and this has been consistant for the past couple of years.
Page Rank on domains: olddomain.com - PR4 newdomain.com - PR3