Steps to reproduce:
1. Create the following program and save to disk as 'us.vala':

using GLib;

public class UShortTest : Object {
  private ushort _us;

  public ushort us {
    get { return(_us); }
  }

  public UShortTest() {
    _us = 0;
  }

  public static int main(string[] args) {
    UShortTest ust = new UShortTest();
    stdout.printf("ust value: %d\n", ust.us);
    return(0);
  }
}

2. With Vala 0.7.4 run "valac us.vala".  A crash occurs.
3. Remove the “: Object” from the class declaration.
4. Run “valac us.vala”. No crash, executable is compiled and it runs.

Stack trace:
Wednesday, 2009-Jul-01 at 03:31:12 - mbt@zest - Linux v2.6.30
Ubuntu Jaunty:[2-55/10577-0]:vala> valac us.vala           
glib-2.0.vapi:181.1-181.20: error: The value type `ushort` doesn't declare a GValue set function
public struct ushort {
^^^^^^^^^^^^^^^^^^^^

** (valac:4568): CRITICAL **: vala_ccode_identifier_construct: assertion `_name != NULL' failed
Compilation failed: 1 error(s), 0 warning(s)


Other information:
This error only occurs when the class derives from GLib.Object; if the class does not derive from GLib.Object, it works just fine.  I have not found a workaround for this issue while maintaining the necessary data type.