I saw this posting on another (nameless) board. I found it very helpful for understanding what is going on with getting data to work on my 300 and maybe you will too. It appears to be an insider posting.

"I have a few tips about getting online with a Treo 300 when you are having problems with activation:

1. If you forgot to turn off your old Sprint phone and you got the weird activation SMS message, you should be good to go. The internal systems at Sprint have been turned on and your phone should activate properly when you try to connect using Blazer. Item 3 or 4 may still affect you though.

2. If you get no SMS message but you get an Error code 67 when you try to connect using Blazer or any other Internet application:
You are not yet correctly provisioned for data in the backend systems at Sprint. Call Sprint support and ask them to turn on your 3G data services.

3. Error code 98 when trying to use Blazer. This means that your data provisioning is half way thru but you have to wait a couple of hours for the other half of the provisioning to finish. Be patient and you may very well be connected next time you try to use Blazer.

4. Sometimes provisioning 'over the air' fails half way thru and you can tell this has happened if you go to the Prefs | network panel of your phone and you see a username which reads 'Sprint-username'. Going to the web portal to reset your username and password retriggers the sending of the username to the phone. There are system updates going on this weekend (8/17) and it may be worth waiting until Monday to do this.

5. Your data provisioning (getting on the Internet for the first time and Sprint turning on the backend systems and sending your phone the right data) will fail if the date and time are not set correctly on the Treo 300. Actually it is just the date but it makes sense to have both set. Go to Prefs | General if you need to check it.

6. It is possible for your network settings to be programmed manually or via a downloadable PDB file containing the network settings. You just have to add a username and password. There are a few variations of the settings depending upon your region. This may become available from Sprint as a way of provisioning data if all else fails. It is not currently available because of confidence in the over the air method being fixed satisfactorily very soon.

As with any new service, there are early teething problems. I hope this helps to smooth the way for those of you with problems."