In case your Google RSS News Reader Widget should have stopped updating,
this may come from changing SD cards without a cold reboot
(I think the widget creates the cache at hardware boot-time only).
In order to fix this:
Just shut it down and take out the battery for a moment;
it should be updating again after rebooting the device
(once the cache directory was created on the new SD card).
In case you might be looking for a more advanced RSS reader client,
one of the best alternatives might be gReader, an unofficial Google Reader Client.