There have been a couple of changes to both the Realspace and Warp probes.
If you enter an invalid sector name, a sector owned by the Federation for the Warp Probe or an SG Sector for the Realspace Probe it will revert to a Sentry Probe.
The Realspace probe is a one shot probe now. If will try to move directly to the sector you indicated. Make sure you have large enough engines or it will just sit there and notify you of the problem in your Probe Logs.
When either the Warp or Realspace Probe reach their target sector they will change into a Sentry Probe.
The Warp Probe randomly follow warplinks looking for the target sector. If it enters a sector without warplinks it will change into a Sentry Probe and just sit there.
Probes are also so small they can completely avoid ALL mine fields no matter how big they are. Only fighters can possibly detect probes and destroy them but they are hampered in detecting probes because of their small size.
Oh... Warp and Realspace probes should now be moving around the galaxy.
One final new item. Warp probes now leave a trail just like a ship as they move around the galaxy.