chalk brush problem

[squashchap]

One of my favorite brushes -- the chalk brush -- has suddenly, and for no apparent reason, decided to change its characteristics. Instead of the nice granular stroke I'm used to, now it comes out heavy and smeary, with no granularity at all. Nothing I've tried so far makes any difference. Even when I load old sets of brushes, the same thing happens. I'm using CS3 on a white iMac, OS 10.4.11. Any help welcome.

 

[SeniorS]

Reset preferences Adobe Forums: How to delete/reset Photoshop...
Had problems with brushes by my own, that helped.

 

[squashchap]

I'll give it a go. Many thanks. I appreciate your help.