Node Relativity can't handle underscores in content type names

Inside 'Link operations' a 'Create new Solution' appears, but it doesn't creat the correct content type. Actually, it doesn't create a link at all.

My set-up:

• Drupal 6.12
• Relativity 1.2

I am using custom content types, created with 'admin/content/types/add':

• Conflict (content_ct)
• Solution (solution_ct)

In this case, it should be possible to attach one solution to different conflicts.

Node relativity, Regular settings:

• Node types that can be involved in relationships: Conflict & Solution

Options for Conflict (conflict_ct) nodes:

• Parental Ordinality: none
• Allowable Child Node types: Solution

Options for Solution (solution_ct) nodes:

• Parental Ordinality: one or more
• Allowable Child Node types: [nothing]

Symptom
The following links are correctly displayed in 'Link operations':

• Create new Solution (node/add/solution_ct/parent/2)
• Attach existing Solution (relativity/listnodes/solution_ct/parent/2)

But the 'Create new solution' does not send me to a 'Create Solution' page, but to a generic 'Create content' page, that looks like 'node/add' without the option of adding a solution_ct. (Note, that it is correct not to show 'solution_ct' in this list, because I disabled "orphan" nodes for this type in Parental Ordinality. But I shouldn't be shown this list in this context, in the first place!)

When I create one of the listed content types, I get exactly that, a new node of this other content type, and it does not get linked to the "parent" node (which is correct, because I didn allow these types in 'Allowable Child Node types').

I've tested this with different user roles, all have the rights to create 'solution_ct' content.