the error message is a bit misleading in this context, but:
to create the elevation diagram, the plugin needs to parse
the gpx file. If you set "read track infos" to "no",
it will not parse the file and thus you'll get no
elevation diagram (and as a consequence, it can not be written either).
Simply set "read track infos" to "yes" and all should be fine.
changes: in the Advanced Options, you can now turn Warnings shown by the
plugin on or off. Default is On (so same beaviour as previous releases).
A brand new feature are "Custom Map Layers" - Bing Maps, anyone?
Beyond the 8 predefined map layers (OSM/Google) you can now have
practically any map layer that works with OpenLayers.
I have written some
on this feature,
there you will find instructions on how to use MS' Bing Maps (if you want).