Hi Guys,
I have made a comment about this problem in the bugs list at
http://bugzilla.zimbra.com/show_bug.cgi?id=14417#c8
I have posted some sample code which worked for me in main head version.
I also developed a sample zimlet which tries to do a post to qpmp.com test PHP page when it is clicked in leftpanel. 'post.
js' file inside the zimlet contains the code to post through proxy service using sendRequest of ZmZimletBase which in turn uses AjxRpc methods. The response that comes from the test page is alerted.
You can find the sample zimlet here
http://bugzilla.zimbra.com/show_bug.cgi?id=14417#c10
Please install this zimlet in your Zimbra build and let us know whether this works. In case of error, let us know about the error (javascript error / response content) so that we can narrow down this problem.