The message "Push Throttled" appears on your TouchDown home screen
Push will throttle itself if it pings your server 5 times in one minute without any kind of response. This can happen for a variety of reasons.
Push throttled is a safety mechanism to prevent your battery from running itself dry by letting TouchDown continuously ping your server without any response. It should automatically turn itself on in about 8-10 minutes to try push again. A few common reasons for this can be a busy server, not enough bars or perhaps not a strong enough signal to Wi-Fi. The number one reason for this is a problem with the server where it refuses to let you connect due to a large message box. One way to prevent this would be to archive older messages off using Outlook's archiving functionality.
Also as a preventative measure you might choose to go to your advanced settings and select a shorter period to sync (for instance, if you have all days of email and appointments set to sync, you would be much better off to sync 1-2 weeks of mail instead, and also perhaps 1-2 months of appointments). Often times, running the quick configuration wizard will fix this error, but if it continues to reoccur you will want to change the settings mentioned above.