Flash is extremely easy to learn.

It took me a day to be able to use it.

Around a month to be able to use it easily without any problems.

And about 3 months to start experimenting with different animating styles, tools, and Frame-by-frame rather than tweening.

And then the rest of the time was just progressing skill-wise and perfecting my style.

Not exactly 'problems' as such, I just knew how to do most things with the program by then.

Before then I wouldn't have known how to use easing or masks, etc.