Greetings! This is my first post. I got my P900 about 2 weeks ago.
I get "Not enough memory" message from time to time. My guess is that RAM is too full to activate a new application. Is there a way to close everything? So far, I have been turning my P900 on/off. Thanks for the help.

Install this software, it's a freeware and it close your apps and free memory
You can find it here
Several bits of software offer this functionality.
If you are running 'Handy Day' or 'Tracker', then these have a mode for it,
however,
I suspect that the '900 does some form of internal cleanup as this error is raised; several times when this has happened to me, I have gone to the task manager only to find all the apps have already closed.
Try launching the app a second time after the message, and it will seem to work.
Thanks all for the reply. I did get Handy Day 2004 and I see the feature. However, close all doesn't work at times. My RAM remained at 94% and I had to turn the phone off and on again. Anyone else having this problem? Will Switcher work better than Handy Day 2004? Thanks again.
Check also the files on C -disk (internal memory). If you have too much data stored there, it may cause this. Remember that the internal storage is the place where applications are run but also where data is stored. Move your data (images, videos, sounds, etc) to the External memory (D-disk).
i have this problem too...
you can use SMAN
SMAN doesnt always solve this problem. I get the error message usually when trying to rotate a pic in the Picture Editor, and getting SMAN to flush everything but itself doesnt always work... i get 5.9 MB left after a flush and I can still get that message...
try geting the latest P900 sw, i havent experienced it since..
One good way to increase your available RAM is to delete the TEMP files located in c:/system/data using an application like QFileMan.
After deleting files labeled TEMP$$$... I regained about 2MB of free space.
Good luck!