UPDATE: I just realized ww25 is not available from the downloads page anymore.. its getting a "404 error - page not found" when I click on the 2.1 firmware link.
Hopefully that's a good sign.
btw, I strongly believe firmware releases should be made available, even older ones so that people can choose which to download.
You should try with another browser and/or cleaning the cache, I just checked the link and it’s still working for me. Regarding your first issue, I suggest you to use the flashall method instead of reboot ota. This should solve your problem. The process is explained here https://communities.intel.com/thread/59757.
In these two links you can find older firmware releases, in case you need any.
I encountered the same issue, 'reboot ota' does not seem to work with the ww25.5-15 image. flashall.sh was the solution for me. Just remember you need to run it with sudo, otherwise it just reboots the board without flashing it. I posted more information on the associated thread at https://communities.intel.com/message/317683#317683
I encountered the same issue too.
'reboot ota' and flashall.sh were not work with the ww25.5-15 image. I tried typing "configure_edison --latest-version", and that command returned "146".
Have you tried the flashall.sh with sudo?
By using sudo, I was able to upgrade to ww25.5-15 image.
Sept. 17, 2015, ww25.5-15 image
Upgrading with 'reboot ota' doesn't work.
Upgrading with CDM v2.10.00 WHQL Certified.exe tool doesn't work.
1. Download & build xFSTK: Building xFSTK on Ubuntu 14.04 (32-bit) for flashing Edison
2. Install xFSTK.