For the past couple of weeks, every time I attempt to reply or forward a message from my handheld, I get an error message that reads: "Mailbox couldn't find original message, if forwarding or replying please resend the message."

Have you talked to the carrier? I have had a number of wierd problems in the last few weeks with my 7230 that I've needed to call T-Mobile about, then they do something on their end and it magically starts working again.

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Mike - Been Converged?

As stupid as this sounds, you can't reply or forward a message that has been deleted from your PC Inbox. If that's not the case, perhaps generating a new security key via the Desktop Manager or a device reboot would help.

I hope this happen due to some installation errors. Please write to below mention email address eCellSupport@dynoplex.com
I hope they can help you.