I am experiencing the reknowned red 'x' when trying to send email from my Blackberry device. I can confirm that incoming is working fine, and that communication is working as when I add an entry to the calendar it updates within exchange.
I am fully aware of the many issues and permission situations surrounding the Blackerry Admin SendAs issue.
I have read through the BES setup advice and followed it to the letter.
I can confirm that the user does not belong to one of the protected groups and that the account shows the BesAdmin account having the 'Send as' permission, even after a few hours! So all is fine here.
I have also tried the 2 resolutions here
(just in case) with no effect.
I have the firewall to allow 3101 and 3500 through to our BES. The BES is on an independant server, exchange is on an inependant server and both are free to be restarted as and when required.
If any other info is required which I have not stated here, please ask.