I just did a test of this and both user and relationship fields are saving string values in quotes in both the usermeta and postmeta table. Do you have any other plugins installed or filters created that could be interfering with or modifying the values of these relationships?
This is actually a function of serializing the data before it is saved, so I’m a little confuse as to what could be causing it. In fact, the second value you posted a:1:{i:0;s:3:777;} will not unserialize and causes an error.
