Great in depth info
http://www.blackberry.com/btsc/dynam...C&kcId=KB14320
Ok I keep seeing this problem popping up, so here’s an all in one Guide to Fixing Disappearing SMS/MMS/E-mail/Call Log and all your other things that seem to disappear.
Reason for it. You’re running out of Device Memory, therefore your pearl Dumps what it doesn’t need. Your messages
Try these steps. Not in any certain order.
Closing Open Applications
ALT+Escape/Back Key
Make sure you haven't left applications open.
There should be 5 applications that are always open.
Default 5:
Phone, BBmessanger, Browers, Homescreen, and Call Log
You may have other 3rd party applications that may have to run in the background, but most can be closed.
Auto Delete ON/OFF
Under Messages:
Select Menu/Blackberry Button
Select Options
Select General Options
Keep Messages: (Shortest is 15 Days, Longest is Forever)
Battery Pull
Pull out battery and leave out for 30 Seconds.
(I do this at least once a week) Just for safety and memory leaks.
Check How much free memory you have
Options -> Status -> File Free: XXXXXXXX Bytes
Make sure it's not low.
Clear Event Log
Press ALT + LGLG
Menu/Blackberry Button
Select Clear Log
Clear Browser Content Cache
Open up your Browser
Menu
Options
Cache Operations
Clear Content Cache
Delete unwanted Applications to free up Device Memory
By using your Desktop Manager, and Application Loader
uncheck unwanted Applications also unused Language Packs
Update your OS http://blackberryforums.pinstack.com...rade_your.html
This is a link to a list of Blackberry OS by carrier.
http://blackberryforums.pinstack.com/3311-blackberry_os_software_links_carrier.html
Remember that OS's are not carrier specific, and you can use any OS from any carrier as long as it's for your model of phone. Do this at your own risk. If you have to return it at anytime you may void your warranty. You can always reload your carriers version, but that's a whole other process. IF you do use another carriers OS remember to delete the
vendor.xml file located at
C:\Program Files\Common Files\Research In Motion\AppLoader\(your current OS) after installing the OS and before plugging in your BB.
*Most importantly if you have been storing Media on your phone without a Media Card. I would suggest getting one. Remember you
only have
64mb of phone memory and the OS will take up about 20mb. So you're working with only 40mb of free space! That's nothing.
BUY A MicroSD card!!! OS 1.103 supports 4GB now!! Hooray!!
If you need help inserting it go here;
http://blackberryforums.pinstack.com...rosd_chip.html
I hope this helps everyone. If I'm missing any other tips let me know I'll edit it.
*another explaination
RIM has identified a design problem with the way that controls within the media application have been implemented. In the media options ("Media Application" > Pick an application such as Pictures > [BlackBerry Menu Key] > "Options") there are two settings:
“Reserved Pictures Memory” – Default Value = 10 MB – This setting reserves memory for Pictures that the customer may take. It blocks off the memory, reducing the “File Free” amount that displays in “Options” > “Status”. This guarantees that the customer will have memory available and will not overwrite email messages within the memory setting set.
“Device Memory Limit” – Default Value = 20 MB – This setting is a safety water mark. It prevents the customer from placing more than the specified amount of memory in their content store (pictures, ringtones, music, etc.. in device memory)
The implementation problem with these settings is that the “Reserved Pictures Memory” setting does not prevent the customer from going beyond the specified amount of memory. That is to say, if the customer has it set to the default value of 10MB, they are not prevented from taking 15MB of pictures for example. The only setting that will limit them is the “Device Memory Limit” setting.
The 20MB default value for this setting is a bit high as typically after loading the handheld software, the memory available is about 20MB. If the customer has a number of contacts, calendar entries, tasks, memopad items, emails, etc… they could have less than 20MB available. This means, with the default settings, the customer could fill their content store to the point that Low Memory Manager activates in an attempt to free up new space by deleting emails and call logs. If approached by a customer in this situation, please recommend that they reduce the “Device Memory Limit” setting to it’s lowest value of 12MB. It is recognized that even this value is high, and the values (including the defaults) are being adjusted in future releases of handheld software.
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Having a large amount of images, ringtones and or games stored in the device may reduce available free memory. If the BlackBerry Pearl's memory is at or near capacity the handheld will begin to delete the oldest Call Log and Text Message (SMS) entries in an effort to free up memory space. In order to prevent this, free memory must be increased.
NOTE: Saved messages will not be deleted.
How To: Stop Disappearing SMS/MMS/E-mail/Call Logs 
