I'm still looking into why 56Kbps dialup gets abnormally-high ping times, but for now my suggestion is to use the original net.ini settings of MinBandwidth = 1000 and MaxBandwidth = 4000. Those limits seem to miss out on some network traffic so it's best to set them conservatively.
Downloads:
Testing Executable and Symbols
Game Assets (no changes since 2011-05-19)
What's new:
* Fixed shell problems after finishing the training and USSR campaigns
- This had the same solution as the USA campaign

* Fixed engineers not going to the APC in Soviet mission 7 ("Reclaim our Base")
* Fixed the engine idle sound dropping out at effect volume 1
* Fixed spurious attack warnings from neutral objects
- Neutral sources are now treated as friendly (as in 1.4)
* Fixed an intermittent error with Weapon on startup in MP in the Testing build
* Fixed missing player stats in net escape screen
* A user-controlled vehicle with no pilot works properly:
- BettyVoice can use vehicle nation as a fallback
- Disable eject control (though maybe it could be "self-destruct"?)
- Enter "death cam" view and start respawn on death
* In MP Strategy, deduct a life upon death instead of on spawn
* Net escape dialog monitors scores and win/lose conditions
- Refresh the score display when something changes
- Pop up the appropriate message on win or lose
. "You won" (multi_common/you_won)
. "You have been eliminated!" (multi_common/you_lose)
- Remove the back button when the game is over
* Player numeric ids increase by 1 instead of 4
- Anet allocates four per machine for some reason...
* Fixed issues with /mute and /unmute commands
- In-game versions actually work now

- Shell versions work when using numeric id
- Mute works between pre-game, in-game, escape, and post-game
* Updated ConstructionRig power check
- Now includes ShieldTower (for custom IA maps)
- Uses the same distance check as powered buildings
* Preliminary implementation of high-ping auto-kick
- Default threshold is 2000ms
- Override with AutoKickPing in net.ini
* Increased Entity limit to 768
- This should help with high-population maps like Europa Bridge
* Fixed airborne powerups warping crazily in MP
- This was a problem with the network compression of object positions
* Fixed bullets expiring before hitting deployed vehicles in MP
* Fixed players sometimes ending up at the same spawn point
- The host only sends out other spawn points after picking its own
* Reduced the size of PowerUp net state
- It now uses the same compression techniques as HoverCraft