| Code | Meaning | Applicability | Notes |
| 0 | No error | All | |
| -1 | Bad Message Type | All | Only send one of the supported message types listed in dlg/resman.h |
| -2 | Port already active | Ports | Don't activate the same port twice. |
| -3 | Port not active | Ports | Deactivation and locking requires an active port. |
| -4 | Resource not locked | All | You'll see this if you used the wrong password or if you're going for an "immediate" lock which fails. |
| -5 | ResMan not active | All | You'll get this if DLG's resource manager, ResMan, is not running. This probably means you don't have DLG running, either. |
| -6 | Out of Memory | All | |
| -7 | Area in Use | Areas | You'll see this if you are attempting to get an exclusive lock on a message or file area, but someone's still in it. Always count up the users in an area before locking it. |
| -8 | Bad Area Number | Areas | You'll see this if you are attempting to get a lock on a message or file area that does not exist. |
| -9 | Area Empty | Areas | This tells you that an area has no users in it. |
| -10 | Language does not exist | Language | The requested language does not exist for the module specified (if specified). |
| -11 | Nonexistant resource | All | The requested resource does not exist. In the case of ports, ActiveatePort may do the trick. |
| -12 | Resource in use | All | |
| -13 | Can't load menu | Menu | The specified menu cannot be locked. It might be in use. |