I could just be seeing things that aren't there. However as a vocal opponent of this sort of surveillance, it would make sense that I would be caught up in some sort of filter especially as the hunt for Snowden continues.
(So note: If you are listening I think you might be. I am a patriot, as I believe Snowden is. I have not provided any active assistance for him, but I applaud those who do. My wife thinks I am too political but at some point my loyalty to my country, the United States, compels me to stand up to this sort of thing.)
Google chat messages can be delayed for any number of reasons, ranging from internal glitches to "Your network connectivity was bad at the precise moment the message was attempted to be delivered, thrice, and it retries at exponentially longer intervals."
It's obvious! After all, spy rule #1 is "make sure your subject knows he's being spied on by marking his messages as 'infringing or spam'". And it's totally impossible that the visa thing coincided with this.