Can you check whether you have the following

HKEY_LOCAL_MACHINE\SOFTWARE\KVS\Enterprise Vault\Mobile Search\Install

If you don't, can you check for the existance of a string called "InstallationType" and "InstallationPath" that points to the place where you installed? (i.e D:\Program Files (x86)\Enterprise Vault Mobile Search)

Also what version? base? SP1, 2, 3, 4, or 5 etc?

The registry key you specified doesn't exist:   

It does exist in the following location:

HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\KVS\Enterprise Vault\Mobile Search\Install

This is EV8 SP5

k that sounds normal,
would you be able to run a Procmon and find out which Registry keys its looking for?

I ran a Procmon and do not see any registry key entries being parsed.  I've tried using a browser on the local host, and I have tried from a seperate workstation.  I can attach a procmon if you like, but I didn't find anything and was very thorough, unless I don't know what I am looking for.

You ran the dtrace on the server that has the mobile search installed right?

We'd probably be looking for w3wp getting a NOT FOUND when attempting to read registry keys
if you want to put the Procmon up here, i'd be happy to take a look

This is what you might be looking for.  See attached screenshot

possibly, were those queries succesful though?

The browswer always returns the following error:

Installation registry key not found, Please contact administrator
 

Is there anymore information that I can collect for you.  This was a standard install straight from the installation package, and I only had to answer a few questions (authentication, DNS Site Alias).

The OS is Windows Server 2008 64-Bit.  As per my previous posts, the following key doesn't exist:

HKEY_LOCAL_MACHINE\SOFTWARE\KVS\Enterprise Vault\Mobile Search\Install

In the registry it is under the following:

HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\KVS\Enterprise Vault\Mobile Search\Install

Create the same registry keys in:-

HKEY_LOCAL_MACHINE\SOFTWARE\KVS\Enterprise Vault\Mobile Search\Install

Does that stop the error.

This maybe a bug whereas the registry keys are created in the wow6432node location but the code is still looking in the x86 location.

Additionally I do not think this is anything to do with your particular issue but as per the latest compatibility charts it is currently not supported on Windows 2008:-

b. Enterprise Vault Mobile Search is supported only on Windows Server 2003 SP2 (32-bit and 64-bit).

Once again, thanks for your support.  I will get the client to rebuild the O/S and proceed from that point on.