BB Curve :: Deleting Apps Doesn't Free Up Memory

Although I've not downloaded any applications for a couple of months, my free space has declined to less than 5 MB on a regular basis. I store no photos, chats, or emails on the internal memory, just the memory card, and just to see if I can fix things I delete large emails as they arrive to try to stave off the inevitable "0 KB Free" message. Lately of course the BB has been deleting emails and chats, apparently to regain space.

The last time the delete checklist popped up -- "you're about out of memory, why not delete some of the installed apps to retrieve space?" -- I deleted Sprint Navigation, which said it was taking up 71MB. I figured that would give me a lot of breathing room. It completely deleted, I hard-rebooted the device, and... no change to my available memory. I'm still losing space. As a matter of fact, after deleting it and receiving that message, I thought maybe it doesn't understand, so I tried reinstalling it and got the "insufficient memory for installation"! So now I deleted something that's potentially useful -- and worked -- and can't put it back on even though it was just deleted!