How can I take a photo of a lit fluorescent. All photos I took yet are blurry, even with the macro mode... 

Are you using a tripod? The camera may have to be very still to get a clear pic.

I wanna say that the camera cannot focus the tube when lit (Very handy )

Can you focus first before lighting the lamp?

DumBulb: Yeah, no problem when the tube is not lit...

I don't think he's dum! 
If you have seen my F15T8/WW lit the shot is very clear! I adjusted the exposure first, so it didn't come out as a white blob

Thanks guys, but finally I found why I can't and it's really simple: I was too close of the tube! 

There ya go!! Hopefully we will see your lit tubes!

I noticed my camera can't focus at all on magnetic-ballasted tubes, but it works fine with electronic-ballasted tubes. Anyway thanks for your help!

Also, try using forced flash, it may help. I have the same issue, and try to get focus on the side of the fitting, as most autofocus has problems with too much light.