have u tried installed task management tools like JBTaskman before to your phone? if you did, i think that app can help u in tracking your available ram.
i was a N81 user before i changed to N82, so i understand what you are saying. N81 has really little internal memory, after installing ngage + nokia maps, it really has around 5MB left. I am not too sure about your situation as i never installed nokia maps 2.0 last time.
restarting your phone doesnt really affect your phone memory(C:) apart from the caches...as i mentioned, a fresh boot for N81 after v21 firmware is around 30MB RAM available to use, as for how much is left on your phone memory, it's entirely based on what you have installed.
as for your situation right, i really not sure, maybe you can try use apps like jbtaskman to monitor your ram usage first.
@andrekua, bufung, aspire2006: can we please don bring that whole ram sage up again everytime we see the word 'ram' in this thread?
I was just explaining ROM vs RAM nia...