Many of my old examples for PGF plots do not work any more. I think the problem is due to this. Does anyone know why 11.10 use the old version of TeXLive?
As far as I understand, the main reason is that no one did the work to package TeXLive 2010 and 2011 for Debian/Ubuntu.
See Ubuntu Bug #712521: [Needs packaging] TeXLive 2011 (especially the comments) for some background information.
The current advice (from the TeX community) is to install TeXLive 2011 yourself, either instead or additionally to the TeXLive 2009 from Ubuntu.