It doesn't necessarilly mean there was a problem at one of your systems, it could have been any kind of problem on "the internet" between you, that caused your systems not to be able to communicate with each other for a while. If you want to get to the bottom of this, you could investigate log files. Both of you just (and only) saying it wasn't a problem on my system, means that at least one of you didn't look at his log files to carefully (or don't want to share what they found). There must be clues in the logs...
