Microsoft Business Solutions Navision 4.00 was released in 2005. Service Pack 1 follows later the same year including a new Navision Employee Portal as a replacement for the Navision User Portal.
Same year Microsoft announces Navision 5.0 as the version with a completely new user interface to be released in late 2006.
On September 6th., 2005, Microsoft announces that what used to known as Microsoft Business Solutions going forward will be branded as Microsoft Dynamics.
At the same time the name Navision is changes to Microsoft Dynamics NAV (not nav but n.a.v. - with all letters pronounced).
In 2006 an delayed Microsoft announces that the new user interface will not be part of Navision 5.0, but instead it will be released 6-12 months later as Microsoft Dynamics NAV 5.1.
So when version Dynamics NAV 5.0 finally was released in March 2007, it was without the new client.
It did have many new application features such as a completely redesigned Job module. The job module had basically not changed since the release of Navision 3.01 (the character based version in 1990).
Again in 2008 Microsoft announces more delays with the new UI. Dynamics NAV 5.0 SP1 is released March. Again without the new client.
The new version including the new client will be called Dynamics NAV 6.0, but is to be released later in 2008. Just a few months later they announced that it would be called Dynamics NAV 2009 and be released in Q4 2008.