Dear mumbai_techie,
Venus as the karaka for the Navamsa chart and placed with Rahu in the 8th is not an auspicious placement.
Your wife is currently running Merc/Venus until May 2012.
especially with Sun-Sat in the Navamsa lagna
In Navamsa chart 6th lord in 8th does nt give any vipareeta raja yoga etc., - But can lead to break up or separation due to fights or arguments.
I would recommend that you both restrain your arguments since in this period things could get out of hand.
Mercury in the 7th in Navamsa can lead to arguments, discussions etc.,
Hope this helps
Shrikanth