[AccessD] A2K: Error 3343 When I install Backend on server

Hello all
I have a FE/BE app setup.
When I install the FE on my local DEV machine and put the BE in another 
directory on the same DEV machine - all is OK the app works fine

BUT...When I put the BE on a server and put the FE on my local DEV machine and try to open the 
usual screens that work finer when it's all local I get the error msg

Error 3343 - Unrecognised database format S:\Truman\Truman_Data\Truman_data.mdb

The S: drive is a valid server drive only I have access to. I have Admin permission level i.e. full read and write permissions

The data base MDB file is valid and is a recognised format - when I copy the MDB file in question from the server and place 
it on my local machine then connect my FE to - all is well. So it's most likely not the BE MDB file.

Any suggestions?

Many thanks

Darren