A Pilot using an iPad2 could not get a commercial chart maker's iPad APP version 2 to load correctly; became distracted while taxiing for takeoff without an airport diagram; and had a runway incursion.

Narrative

Possible incursion of Runway 12 at SAC while proceeding north bound on Taxiway M. Reviewing this incident in my mind I can identify a number of causative factors that led to 1) Complacency/breakdown in vigilance and 2) A loss of precise understanding of airport layout. This was a Part 91 flight of tail wheel experimental aircraft. I do operate a twin turbine under Part 135 and have instruction responsibilities with our company in that aircraft so feel especially responsible in this situation. I emphasized at a [recent] pilot meeting the need to be vigilant while taxiing and always have a taxi diagram available for reference. Failing to be disciplined with regards to sterile cockpit rule after copying taxi clearance and even while taxiing was contributory. Probably the largest factor was a failure of commercial chart maker iPad APP version 2. Although I've been using another iPad APP and commercial chart maker's version 1 product for a while this was the first trip while using version 2. I copied clearance on the Scratch pad. (Sidebar: In fact I got home and remembered I could take a screen shot of anything on the iPad so I did of the scratch pad which had the clearance still written on it. It had 'b m 16 280 125.25' which was my shorthand for information number; taxi B M cross 16; departure heading of 280 frequency 125.25). Then after a number of tries attempting to open the commercial chart version 2 airport diagrams we determined that the most recent update - or for whatever other reason the database was corrupted and no airport info was available for any airport. I referred to the other APP's airports page with weather selected and used that to setup my comm radios after start. My interest in keeping things moving at this point was actually mostly heat related as I didn't want to overheat myself or idle at length which would cut into a buffer of relatively low CHT for takeoff to accommodate the expected high CHT's on climb in warm weather with a tightly cowled aircraft. After copying the clearance my mental image of the airport being a relatively simple lay out with two strips of pavement interfered with literally and accurately processing required actions (my biggest mistake). I'm pretty sure the Controller actually said taxi Bravo; Mike cross 16; hold short 12. I bet I even read back hold short 12 but was thinking of that as being the departure Runway (20) so didn't even write it (the hold short 12 part) down on the scratch pad. During taxi out there is limited easy visibility over the cowl and when we crossed 16 I was thinking home free to 20. Only after the Controller said cross 12 hold short 20 (and my dutiful read back of clearance) did it dawn on me that I was just crossing 12). We may have even been technically legal upon crossing 12 - I really don't know. To summarize; a number of factors led to this lapse in situational awareness. 1. No sterile cockpit while taxiing. 2. No airport diagram open (probably as a result of impatience with the commercial iPad APP version 2 and the unsuccessful attempts to open it with that program.) 3. Mistaken mental picture of airport layout. 4. Mistaken interpretation of clearance (expecting cross intersecting runway and hold short of departure runway was my mental interpretation) even though I probably gave correct read back.4. Tail wheel (leading to tunnel vision and devoting attention to straight ahead taxi after crossing 16). Clearly I should have stopped the above chain by not moving till I had the airport diagram open and understood before moving. There was no conflict or possible conflict that I was aware of or made aware of. As a foot note the commercial chart maker iPad APP version 2 problem was solved by turning the iPad off and then back on. Wish I had taken a screen shot of the 'database' before performing this restart.