Trouble Syncing with Android

Hi all ... I am relatively new to Zimbra and all of a sudden I am having an issue with activesync (Corporate Sync). Some of my users started complaining the other day that their mail stopped syncing. So I added an account to my phone (Droid Pro) to test. I am able to add the account with no problem, but when I open the mailbox to try and sync it says "Connection Error". I can send emails with no problem at all, but for some reason it just won't receive.

Any ideas would be greatly appreciated as I seem to be striking out. Nothing changed on the server at all and I know that it WAS working just fine up until a few days ago. We are running Release 5.0.15_GA_2851.RHEL5_20090310165728 RHEL5 NETWORK edition.

Thanks for your help in advance.

UPDATE: I downloaded and installed the Android fling app and that works. So it appears as if it is only the native mail app that is not working. Any ideas?

Nevermind on this ... I bit the bullet and upgraded to 7.1 ... problem solved. Thanks anyways!!