Flashing doesn't void your warranty, they are just not under any obligation to help you with support questions if you flash your device to something other than the proper versions sold with the phone, so running US firmware on non-us phone for example. Yes they are allowed to charge you to get your firmware back into a state that they can provide support, as you flashing to a non-supported firmware for your phone is not covered by warranty(but it doesn't void your warranty completely)

now to understand your problems

After reflashing the firmware and formatting the eMMC,did you try to use it in this state after this, and before restoring a backup? If yes, did it have the same problem?

Also, do you have a microsd card in the phone? if yes, have you tried removing the battery and the microsd card, and then replace only the battery, leaving out the microsd card, and reboot and see if you still have any problem?

have you used swappolube?? try that out. also if you phone is on for say 4 days or so, it becomes lesser responsive... it is better to reboot..

try overclocking an dusing ulv. PM me if you need help...

nokia is a realtime sucker !!!!

i have flashed my n900 5-6 times in the nearby nokia care its still in warranty dude

As far the 'get stuck' part is concerned, a N900 in mint coditions - i.e. just flashed, no extra app/widget installed - should not have too many hog problems, except perhaps flash running on some website. I never experienced missed calls with the phone 'clear'. Obviously the 900 is born to install stuff, but it is not resilient to much of them!
I made a (technical and boring, very long - http://talk.maemo.org/showthread.php?t=71115) post on the matter, since I like 'geeking' with my n900 but at the same time it is my production phone and therefore to loose calls IS NOT AN OPTION.
Usually it happens when some process hogs the phone and/or you have a very high swap activity when a phone call come in.
If you are not afraid to change some critical parameters, you could try to implement some of the modifications I proposed.
Swappolube could help, but IMHO only in the short term and from a 'feeling' point of wiev so definitively worth trying, other scripts, well... I think that it is better to reboot the phone every night. Alarms will turn it on anyway when you wake up in the morning!
What are your standard use-cases? Did you notice some patterns that lead to missed calls?
I had phone rotation disabled in order to avoid the extra stress related, and it helps a lot to not to miss calls.
Now I have it re-enabled again after all the job reported in that post.

was there ever a solution to this? My phone has just started exhibiting this behaviour.. If I lock the screen (so it's black) and leave it for a long time (half an hour), when I wake it up, or a call comes in and it wakes itself, the touchscreen won't respond to input for 5 - 10 seconds after the screen lights up

The phone isn't frozen, because I can still use the keyboard to do things like CTRL + BACKSPACE to see the running tasks - it's just that the touchscreen interaction has no effect

There's no lag or problem when the touchscreen does respond, it's just as if the touch digitizer is switched off for a while after the phone wakes - kinda like your computer would seem unresponsive if you unplugged the mouse..

As a workaround is there any key combination that will answer a call? I'm assuming as the keyboard still works fine from the first moment the phone wakes, that I could answer calls with the keypresses while the touchscreen is still unresponsive

I´ve had similar problem: Look for ereswap thread to pass your swap partition to a sd card and your problem will be gone since then I think I´ve never loosed a call again

http://talk.maemo.org/showthread.php...hlight=ereswap
http://talk.maemo.org/showthread.php...hlight=ereswap

Exactly. That is the solution. Putting swap onto SD (away from eMMC). And have it cleaned up / defragmented from time to time.
So best approach is to use two swap partitions on SD.

Completely agree, best thing I ever did.
Put two 800mb swaps on the uSD card after the main FAT space.
Works great, after a week or so when swap gets fragmented swapon to the second and swapoff the first. Vice versa the next time you require a fresh device.
Like a freshly reboot device again.

Yep, never lost a call since that double SD swap approach.
With single SD swap still from time to time. Earlier very often.
No lags at all (despite very few during reswapping).

Or greater.
And it is also possible with swap files on first/only FAT partition.

what kind of usage do you have? Mine reswaps daily or even more often (OK, sometime every two days only ).