Its client side. The fix is pretty simple:
1 - Remove the pipe that is causing you to crash
2 - Exit minecraft
3 - Navigate to C:\Users\youruserfolder\AppData\Roaming\.techniclauncher\tekkit\config\railcraft
4 - Open railcraft.cfg with a text editing program
5 - Find the line that contains: net.gui.utility.feed.station=108
6 - Edit that line to say net.gui.utility.feed.station=125
7 - Save
You should be able to now place a new pipe and access the menu.