I was trying to install the on demand plugin and I needed to install python-simplejson and python-numbers.
I was getting errors and the message said try 'opkg update' but when I did it returned a 'wget error 255' for each of the 4 feeds.
Are the feed servers down at the moment? I eventually did get it installed and working by installing with -nodeps. I also had to find a different version of python-numbers as the one I had was giving an md5sum mismatch.
All ok now anyway.