We've had a lot of issues with the login accout for NetMRI getting locked out.  The ID and password are included in the settings and the devices are able to login.  But quite often, for some reason, it will run into an issue logging in, even with devices that it's logged into before.  What could we look at to determine why this is occurring.

The account settings are for the password to never expire and be locked out after five invalid tries.  The account has access to all the devices in NetMRI - and as stated above will error on previously successful devices.

Can you verify that NetMRI is the only device using the NetMRI credentials? Is there any chance that a person is trying to use those credentials to log directly into your network devices?

I occasionally see netmri failed logins in our Cisco ACS logs.  I seriously doubt that anyone here is using it manually.  I think that NetMRI is trying some of the passwords it has been given.  Try increasing the failure count to 10 for its account and see if it stops. This will depend on whether the failure count can be configured on a per-account basis or whether it is a global in your AAA server.