An error of type E_ERROR was caused in line 120 with Business Manager Plugin

Hi,
I am using the Business Manager Plugin and absolutely love it!! It looks and operates great from my end BUT…when a user logs into my site with their own credentials and tries to use it, the following happens:
User logs in and goes to “Dashboard”
Clicks on “View Projects List”
Clicks on “Test Case”
Screen pops up with the heading “Settings” and body: Assigned To; There has been a critical error on this website. Please check your site admin email inbox for instructions”
I then received an email that begins with `An error of type E_ERROR was caused in line 120 of the file…
What’s going on? Is this fixable or must I stop using this plugin?