If I use a Japanese GH1 in the UK, will I get a flickering strobe effect under electric lighting at 24p and 60i?

Why is the frame rate different for PAL and NTSC anyway?

I have noticed that if I set my Canon HF100 to a very fast shutter speed, I get the strobe effect under electric lighting in NTSC regions, but not at 50i or 25p.

Anything to worry about?