Specify the service thread timers in ms instead of us.

diff --git a/misc/system.c b/misc/system.c
index dbb71a0..ad5c849 100644
--- a/misc/system.c
+++ b/misc/system.c
@@ -57,7 +57,7 @@
 static void SYSTEM_StartTicks(void)
 {
     if ( SYS_Service == INVALID_HANDLE_VALUE )
-        SYS_Service = SERVICE_AddTimer( SYS_TIMER_RATE, SYSTEM_TimerTick, 0L );
+        SYS_Service = SERVICE_AddTimer( (SYS_TIMER_RATE+500)/1000, SYSTEM_TimerTick, 0L );
 }