Error code 30000 timed out.
I think everyone that's commented in this thread thus far has a different issue. Space_vodka was having client freezes which will cause a 30000 because the connection to the game sever will time out.
Miggs, yours sounds like the server locking up which is something I've been looking into and have a few different bugs for how it's happening in 2.6.1
Xious, yours might be a server crash if it happens every single time you get to that same mission though I'd have to be watching the server when it happens to know for sure.
Unfortunately this error happens for a wide variety of reasons. Some on our end, some not. Though as we get closer to beta, the number of reasons it happens that are on our end will go down.
Source - Quote #7542928