A while ago, I was tracking down some NaNs in accelerometer-based code (smoothing device orientation for an OpenGL AR view). It turns out it wasn’t my bug — UIAcceleration.timestamp was going backwards approximately every 12 minutes! Naturally, the documentation doesn’t mention anything about this:

This value indicates the time relative to the device CPU time base register. Compare acceleration event timestamps to determine the elapsed time between them.

Assuming iPhone OS is similar enough to Mac OS X, it must be using mach_absolute_time():[1]
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We’ve been making continual minor improvements to Optiscan, fixing some issues with cut and paste and handling of certain types of addresses. Unfortunately a serious bug slipped into release 1.8.2, which hit the App Store yesterday. Apple helped us immensely by fast-tracking approval of version 1.8.3. If you are seeing crashes in Optiscan today, check if you are still running 1.8.2. If so, check the App Store for an update! (It may take up to another couple of hours till it’s fully propagated through their distribution network.)