Paint grasscloth wallpaper????
You can use Glidden Ultra-Hide Gripper to prime it. Topcoat with two coats of Glidden Evermore/Ultra-Hide/Ralph Lauren - in a color and sheen of your choice.
Having said that, painted grasscloth - in my opinion - doesn't look very good - in fact it can look a great deal like faux grasscloth wallpaper - yuck!
Also - you need to test an area first - the chemicals in even latex paint can make the grasscloth come off.
I personally would either decorate around it - or remove it.
If you want a slightly textured wall - check out Ralph Lauren Linen Technique - it is easy to do - and it looks and FEELS! like Linen. Check it out at RLHOME.POLO.COM
I have seen it painted and it looks fine and it is darn sight easier than removing it.
Go for it.