I then change the default "15 minutes before" to show "two hours before." That requires me to click on the 15 and change it to 2. [...] At some undetermined future time within the next few hours, the alert time magically changes to "15 hours." Any ideas?
Possibly, and it differs from Joemikeb's. First off, I wonder if you ever checked the alarm details
after you have set them. If you would, I suspect you'd see that the alert time doesn't change at 'some determined future time' after setting, but right when you set it. Furthermore, if I'm right, I suspect that when you're done with the edit, the alert is not set to 15 hours, but to 12 hours
*.
What happens is this: when you put the cursor after the 5 (of 15) and hit Delete twice, followed by 2, it reads 12 instead of 2. That is because the second hit of the Delete key doesn't do anything. Try it. Once you have that 12, you have to move the cursor over between the 1 and the 2 and hit Delete again. It's this aberrant behavior of that number field in iCal that causes your problem.
*) In the (unlikely) case you do in fact see '15 hours', your keyboard sequence is different from what I'd use, causing you to hit the number field snag differently as well. Even so, the problem is still the same. Hence my suggestion to check after you finish editing (by hitting 'Done') by double-clicking the iCal event.
