Sorry, I've tried this already. I even went as far as doing a factory reset on the device.
I even removed all the switch gear and connected both XP machine and Slingbox with only the router in the middle and it still gives a timeout error.
Win 7, it worked fine. (and when I say works, I mean it works without your hack)
And as far as your solution is concerned, that's a temporary fix. It should work on the LAN without your workaround.
Does Slingmedia test with XP anymore?
Wow, what a ride it has been...
Mind you, this is after I already did a factory reset.
I changed my router (Actiontec MI424WR) to an old Dlink 624 and it started to work!
Still very odd. I then did a factory reset again, and put the Actiontec back as the router. BUT this time I let Slingmedia pick the IP address where as before I was going into the advance menu and specifically selecting 10.19.78.10. Sling picked 10.19.78.254. I didn't see a means to select DHCP.
After I let Sling pick the IP, everything has been fine on my Windows XP machines.
This was AFTER I downgraded my firmware and used a slew of switch and cable configurations, and Slingplayer versions.
There still is something very fishy going on and I think it might be a bug of some sorts, but It may be overlooked since very few people go into the advanced menu, use a 10.x address and use a MI424WR.
Hope this helps anyone else with similar timeout issues.