I do not know what plugin you guys use for you're psp (CFW) but i had this plugin on 4.01m33-2 and now on 5.00m33-3 and this is the best screenshot plugin ever !
It takes a screenshot in about 1 second(or even less) 
And its fully supported with and m33 CFW (I have not tested it on any other cfw),
Preferable 3.71m33(x) and upwards !
Anyways, you will thank me a lot when you will see how awesome this is !
Download it here:
Install Instructions:
All you have to do is copy seplugins folder to the root of you're memory stick !
If you already have seplugins floder with other contents in you're memory stick, then copy each file:
screenshotbmp.prx...game.txt...pops.txt... and
vsh.txt, into the seplugins folder !
And make sure each text document mentioned above has this line in it:
Code:
ms0:/seplugins/screenshotbmp.prx
After you copied all mentioned above:
1. Turn off PsP.
2. Hold R trigger and turn PsP back on.
3. Go to plugins and enable all three screenshotbmp.prx
4. Go back and then exit.
To take a screenshot all you have to do is press the NOTE button
Enjoy ! 