Oh dear! there have been a few instances like this, mainly on the inputs page but also the feeds page. Have you tried to clear the browser cache (you can use CTRL-F5 in many browsers).
are you running the very latest emoncms? See the “Input list doesn’t load” for the latest attempt to fix this.
It could be that the “invalid data” you posted in error is still lurking somewhere causing an issue, if clearing the cache doesn’t work you could also try flushing redis too.