CiviCRM views all empty after update

Since updating to 4.7.24, all my CiviCRM-integrated views are showing empty results.

This may or may not be relevant: When I noticed the dashlets were empty I went to Structure->Views and it just said "Error". The log showed I was getting the dreaded "Invalid Entity Filter" error (See CRM-18504). I found this advice: https://issues.civicrm.org/jira/browse/CRM-18504?focusedCommentId=100018&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-100018 and discovered that I had an empty-string value in civicrm_custom_group.extends_entity_column_value. The advice said to change it to an integer (in this case would be the relationship type id) but I looked at the other values in the table and they looked like 
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for example where the characters on each side are the MySQL representation of a binary value, you know the box with ones and zeros in it. So I took a value from a different field, replaced the integer inside it with the desired relationship type id and updated it to that. It updated but gave me many warnings - one for each row (although I was only changing one row) saying "Truncated incorrect DOUBLE value". Which is odd because the field is not a double but a varchar. Anyway, the Invalid Entity Filter error went away, and no harm seems to have come to custom groups or relationship types when testing them inside Civi, but the views are still empty. 

If someone could shed light on what these binary things on either side of the value are, that would be great.