Rick, you said it compiles in the Setup menu. Does it compile in Developer Console? The former uses the Metadata API and the latter the Tooling API. You can also tell IC to use the Metadata API for Apex by unchecking
Settings>Illuminated Cloud>Validation and Deployment>Prefer Tooling API for>Apex. See if it deploys/compiles successfully with that setting disabled.
In the past there has been at least one instance of the Tooling API reporting a false negative where the Metadata API would compile/deploy properly. It's possible this is another such issue, but hopefully not.
Let me know if you can pick up a consistent pattern for what works and what doesn't. Once that pattern is established, if it's something that's happening what IC is deploying the file, that's mine to fix and I'll definitely address it ASAP.
Regards,
Scott