I'm trying to work on my BSE animation and I set the fps to 18. But everytime I press the enter key to play it, because I want to see how its progressing, it switches the fps to 9.1 fps. Wtf?

You have to hit the "ENTER" key after you set the fps.

Its like

Click to the "change fps field"
set the fps to 18
hit ENTER
click somewhere to timeline
hit ENTER

Is is working ?

seems your getting lag. just ctrl enter and set quality to low

The fla previewing function cuts some fps. just test the movie or drag your mouse on the frames to get a smaller and less effort-investing preview.

Quote from Chunkels

seems your getting lag. just ctrl enter and set quality to low

This worked. Thanks guys .