From FreeSpace Wiki
This page is meant to serve as a repository of recent, common problems with the Source Code Project's FSO releases. If you can't find your solution on this page, so be sure you're using a recent build and that you've tested without mods installed. If the problem persists, try asking in the Source Code Forums.
Random CTD upon starting a mission
Most commonly, this results from using mv_music with an older build (circa 3.6.5). Try removing mv_music, or upgrading to a more recent build, and see if that resolves the problem.
Blue lines are appearing in the interface
This is caused by using both -pcx32 and anti-aliasing at the same time. Try disabling one or the other and see if it helps.
Every time I try to play an OGG, fs2_open crashes
You're likely using an older build. The OGG code has a tendency to pop up with new problems; try a newer build and see if that fixes it, otherwise, report it to mantis.
Fs2NetD tells me I'm using hacked tables!
Unfortunately, all the bugs aren't worked out of tbl validation yet, so Fs2NetD gives this error for any kind of table. In the future, only approved modified .tbl files, as well as the retail ones, will be supported.
Tech Room CTDs when viewing weapons or intelligence
Reset the tech room by entering the Campaign Selection screen and restarting any of the available campaigns. After this the Tech Room works correctly. Common occurrance when using multiple mods.
Some or all of the ships are missing from the Tech Room
To get the ships showing in Tech Room use the same procedure as above. Or press F3 in the mainhall OR press CTRL + SHIFT + S in Tech Room to view all the ships in the game regardless of the campaign progress.