Are you sure that there is only one request sent to the server? You could verify this using Firebug or something like this.
However I strongly suggest to update PrettyFaces to the most recent version. The version you are using is very very very old and the recent versions of PrettyFaces contain many important bugfixes.
What did prettyContext.getCurrentCalculatedUri() return in 1.2.6? The original request URI? In this case you could try prettyContext.getRequestURL().toString(). Or you could use prettyContext.getCurrentMapping() to get the current URL mapping.
I hope this helps.
Do you play Magic?
Get TopDecked MTG, the #1 Magic App, built by players, for players. Free to use, forever.