XBees no longer talk to serial

I just got two XBee S1’s - one of them is a Pro - and the XBee explorer. When I first started using them, they seemed to talk to the serial port; I was able to configure them with Tom Igoe’s XBee Terminal for Processing as well as XBee Terminal Max. I tried to use Cool Term, but with no luck. Once I had the XBees configured, I hooked them up to my Arduinos and tried to send simple on off signals. No luck. After this, they seemed to stop talking to serial. I could no longer get any kind of OK message from any of the serial programs when I typed the “XXX.” They just seemed to stop working. I’m doing all of this on a Mac, so I can’t use XCTU. Has anyone had experience with this sort of thing happening on a Mac?

I’d really appreciate any ideas or help I get with this. Thanks.

not “XXX” but rather +++

oh yeah. ha. oops.