i downloaded the FBM (viewtopic.php?f=61&t=17138) mod and when i use it after a while cortex command crashes and a error window appears. I have no idea what it means so i was wondering if anybody could help me out a bit.

I think that happens to me -On an unrelated note if you're using keyboard only DON'T try to use the pie menu if you have the cursor selected, it'll crash. However CC just tends to crash randomly with various mods - It's an engine screw-up of some sort, I don't know whether it can be fixed within the next build, but there's nothing we can do about it right now.

The Computer Brain is filled with a massive amount of complex coding. Even though it is stable, and TLB put checks in to prevent crashes, things can still slip by when something is that complex. And Cortex Command is notorious for being unstable when it comes to anything done with Lua. There really isn't any fix for it, just follow Seraph's advice and try to avoid what causes crashes.