A Runtime Error 76 initially occurs when attempting to add a new cable type (17th Edition > Cable Data > Add new cable file). The error 76 then occurs each time Hevacomp Connect is opened.
This error is due to Windows security settings.
Hevacomp Connect data is stored within a folder named "IEE", as below. Hevacomp attempts to write to this location when any cable data is changed.
A Runtime Error 76 occurs at this point due to User Account Control (UAC) preventing Hevacomp in accessing this IEE data folder.
UAC instead forces Hevacomp to write to an alternative location (listed below) due to its "Virtual Store" settings. Information about the background of this setting can be found here.
C:\users\<username>\Appdata\local\Virtual Store\....
The easiest way to resolve this issue is to simply disable User Account Control. Guidance on how to do so is available here, or alternatively please consult your IT support.