TarraBelle

Over the past week I've gotten several friending invites that I've attempted to accept. But in three of those instances, when I click on the 'accept' button, the button visually responds, but nothing else happens. The person who sent the invite gets no response. If I send to him the invite, everything works as expected. During the same time period, other friend offers allow me to accept as usual. Any idea what's going on here?