An A319 Captain reported deviating from a STAR because of programming issues with the FMC and distractions which included a wake vortex encounter.

Narrative

Flying the arrival ATC canceled speed restrictions on part of the arrival. While slowing for 10;000 at 250 [we] became high on the approach; selected open descent to make upcoming restrictions; however left 7;000 FT in the FCU for the managed arrival. During the ensuing mess realized we were still in open descent and about to miss crossing restrictions; I turned off the autopilot and attempted to manually fly until properly restoring automation. That's when we encountered wake turbulence from the preceding aircraft. It was particularly strong since we were below profile by approximately 200 FT when we entered it. ATC queried us somewhat and advised us to maintain appropriate altitude for our portion of the arrival; which we attempted to do. While restoring automation I apparently missed something because when we returned to managed descent the aircraft began a shallow descent; descending below profile which was not caught until ATC again queried us and again gave an altitude to maintain until the next fix. We complied; properly restored automation and flew the remainder of the arrival with no further incident. We all have had the identical clearance countless times; we are both VERY experienced Airbus pilots; but this one reached up and grabbed us! Complacency; fatigue; stress all have cumulative affects and I think this is a classic example of this. Just try to treat every one like it's your first.