Activesync to Exchange OTA not working

[jalan]

I am having a sudden problem with Activesync to our Exchange server. Everything has been working fine for months. Then, yesterday, I began to notice when I was physically in the office, that my Outlook mail had new email that wasn't showing up on my Treo. I went into ActiveSync and noticed that my last Exchange OTA synchronization was hours ago. For my settings, I have the schedule as "when items arrive" for all hours of the day. All of my server settings have been verified and are correct.

When I press the sync button to manually initiate a sync, you can graphically see the sync button depress but nothing happens. There is no data transfer activity on my EV icon.

If I shut off the radio and turn it back on, or soft reset the device, the sync works. I can manually sync multiple times. Then, at some point, it will return to the above behavior requiring a reset of the device again.

Last night, I did a soft reset at about 9pm. This morning when I woke up, my last ActiveSync was at 3:13am in the morning according to the log.

Any ideas? Could this be a Sprint network based issue. I haven't changed anything on my Treo - no new software installs that I haven't had for awhile.