Has anyone else come up with this problem?
 
I have.  Here are my games so far. 

-Dragon Quest Wars
-Bomberman Blitz
-Mario vs Donkey Kong Minis March Again! 
-Mighty Flip Champs!
-Dr. Mario Express
-Art Style precipice
-" " DIGIDRIVE
-" " PiCTOBiTS
-" " AQUIA
-" " BASE 10
-" " BOXLIFE
-" " ZENGAGE
-DSi Web Browser
-Flipnote Studio
-Animal Crossing Calculator
-Birds and Beans

No, my DSi is far from running out of memory. 
 
I guess you've been saving a load of images and audio onto the internal memory, rather than on a SD card, which you should do.  
  
EDIT:
 
Delete or move all unnecessary files onto SD.

" No, my DSi is far from running out of memory.  I guess you've been saving a load of images and audio onto the internal memory, rather than on a SD card, which you should do.    EDIT: Delete or move all unnecessary files onto SD. "

I only have 2 games, Flipnote and the browser, so I am a long way from being full up.  You have just 3 blocks left?  What happens after that?  Will you need to delete old games for new and if so, can you redownload for free? 
 
How is Dragon Quest Wars?  It is the only DSi game I really want.