The issue you are seeing with pagers and categorized views is due to a bug in the enhanced view navigator in Notes Domino 9.0. The XPages View Navigator was upgraded in 9.0 to a new implementation to address performance issues with heavily populated view categories.This feature went in late in the 9.0 cycle and while the vast majority of use cases work, some bugs have arisen.
This issue "HBJW95PBZ8" was addressed in Interim Fix 1 for IBM Notes & Domino 9.0 (9.0.0.0) - http://www-01.ibm.com/support/docview.wss?uid=swg21636023 - you can take this Interim fix to resolve this.
Though if you want to change the default behaviour of the View navigation in the Notes Domino 9.0 without installing the interim fix you can revert this behaviour by adding\setting "xsp.domino.view.navigator=ext85x" in the server's or application's xsp.properties file. This will return the view navigation back to what it was for XPages in 8.5.x.
In Interim Fix 2 for IBM Notes & Domino 9.0 (9.0.0.0) - http://www-01.ibm.com/support/docview.wss?uid=swg21640580 - we reverted the behaviour altogether of the View Navigation (MDOY97XJ7Y) as subsequent testing uncovered a few other issues associated with the 9.0 View Navigation feature though not has serious as "HBJW95PBZ8". You can still use this new view navigation and take advantage of the performance improvements it provides by setting "xsp.domino.view.navigator=ext90x".
In Notes Domino 9.0.1, we have addressed all of the known issues with the new implementation of the view navigator so you shouldn't see these issues again.
Hope this helps.