Hi zementmartin,
What other rules do you have in "Design>>Rules>>Electrical>>Clearance"? I suspect there's another rule that is conflicting. Additionally, what do you have set in "Preferences>>PCB Editor>>General>>Metric Precision"?
If it is easier for you, you can save the electrical rules, zip or rar them, and attach them to your post. You do that by selecting the rules in the Design Rules dialog, right clicking, and selecting "Export" from the right click menu.
I looked carefully at a board here, and I don't see any indication of a problem similar to yours. There has to be something in your settings or with your board that is causing this.
Better than just the rules, if you can, zip or rar your PCBDoc file and PM it to me, I'll have a look using my setup, and see if I can identify the source of the problem.
House_Cat