Error Access Denied for List

I have a list for which inheritance is broken, and two SharePoint Groups were created (Read and Contribute).

There are around 30 users in the Read group and 10 in Contribute, all of which are from the same domain, and working properly.

I have two users who are in the same groups, from the same Domains, who are unable to access the list, getting Error: Access Denied.

I've tried deleting and re-adding their accounts but no change.

I've run their accounts through "Check Permissions", and both look good, identical to properly authorized users.

Any troubleshooting recommendations?

Thanks,

Scott