First, I just joined the forum and would like to say thanks to everyone working on FSO, mods or HLP

Freespace is my favorite game and FSO makes it even a lot more enjoyable! I really enjoyed the mods I've played so far.
Now to my topic (I'm not sure whether this is a modding/modeling question):
I'm new to modeling and I'm working on my first model (based on the Homeworld Progenitor Drone).
Currently, I'm trying to put a texture on the mesh. However, it looks rough when viewed in the lab (F3 in FSO), while it looks fine in PCS2 (and Blender). Here are two screenshots with a dummy texture (just some line drawing) for comparison:

(viewed in PCS2)

(viewed in the FSO lab)
As you can see in the first image, the thin black lines are
continuous (as they should), while they are
dashed in the second.
I've tried different texture sizes (1024
2 and 2048
2), DDS and TGA formats, and putting the texture on an existing model. Always the same result.
Why does it look different in the game and PCS2 (or Blender)? Is there any setting causing this effect?
Using fs2_open_3_6_14_SSE.exe, Blender, Gimp and most recent drivers for my GeForce 8400 GS. The debug log doesn't complain about the model or the texture (besides a shield icon warning).