i gt a problem with photoshop

every time i start to use it it wrks fine n then after abt 10 of use it doesnt freeze bt stops me from using any tools. i can use the menues and all but when i select a tool like painbrush it jst shows a normal arrow n nt the tool.

if i save that project then close photoshop n reopen it again it does the same thing bt if i reopen it and create a new file it wrks again for a lil while n then does the same thing.

i tried reinstallin n still nothing. i also tried changing scratch disks and so on bt still nothing.

can somone please help

thanks alot