When I attempt to add users to a survey, I get the attached error message.

How I'm doing it:

1. Select the users to add, click 'Add to survey'
2. Select the survey to add them to
3. I reach a page where I'm prompted to 'Map your participant attributes to an existing token attribute or create a new one'
4. Click continue.....

And BOOM. What is causing this (rather unhelpful) error message, and more importantly, how can I fix it? I've also received an (almost) identical message, except the MS-Sql error message hidden in the html said something along the lines of 'conversion from varchar to int failed'.

EDIT: I should specify that this screen shot was taken a few days ago. We have since updated our Limesurvey to the latest build, but this issue persists.

Unless I'm losing it, the 'edit post' button disappeared since yesterday. Here's a screen cap of the other error message I get.

This seems related.
bugs.limesurvey.org/view.php?id=7196
Could I get confirmation from a dev?

Maybe,

Please test with the last GIT version, and report it to the bug report.

Denis