Sun Explorer version 5.7 was released a few weeks ago, and is available for download from http://sunsolve.sun.com/explorer
As well as the usual list of new features and bug fixes (full list available in the Release Notes) we've now officially added support for uploading via HTTPS through a proxy server, which we managed to miss when we first added HTTPS upload support in 5.5.
Unfortunately one bug did slip through - if you're using either the "scextended" or "alomextended" modules to connect to the system controller on an F3800->E6900 or V210/240/440 over the network, and the SC/ALOM is configured to use telnet rather than SSH then Explorer will fail to connect to the SC/ALOM. The easiest workaround is simply to stay with Explorer 5.6 until 5.8 is released, or just configure your SC/ALOM to use SSH in stead of telnet.