Related Assets in Properties not showing up

I go into properties and relate an asset to the source. I click Save & Close. The source file shows up under Related on the right side. It tells me it was successfully updated but doesn't close. I have to click Cancel. When I go back into the properties for that asset, the source doesn't show up under Related on the right side. If I click Relate | Source again, it tells me there's already a source file. What am I doing wrong? Or is this a glitch in the software?