MapGuide/AIMS runs as a Service: Start > Control Panel > Administrative Tools > Servies
In the Infrastructure Map Server 2014 - in the Log On tab, rather than using the "Local System Account", you will need to log in with a user that is:
1. A local Admin on the computer where AIMS is Installed
2. Able to see the network share where you store your files
Restart the AIMS service...
You can't use a mapped drive - you will have to use UNC path names in the alias.