After installing opera on my phone the memory kept wasting out really fast. After i uninstalled it the memory kept wasting out even when i had no appz installed. I went into a system folder called 'mail' and i think this was causing the low memory. Everytime i sent an email to someone it was stored in there. :( i deleted the folder and now all the memory is back but when i try to access my pop3 mail i get 'system error'. How can i fix this. :(
Not a good idea to go deleting files/folders like that, as you've noticed by now.
The easiest way to fix the situation is with a full reformat (type *#7370# at the idle screen, have your lock code at hand - default is 12345 and make sure you also have a full battery or the phone is on AC).
Unfortunately you'll loose all information (contacts, messages, settings, installed programs).