took my old microSD(4gb) and tried to put in N900 to get photos to my PC. then i noticed that my phone couldn't find the Sdcard. so i took my 16gb sd card to N900 and same thing happened. then i borrowed microSD to SD adapter and tried to get the photos out that way but neither win7 or ubuntu was able to find the cards. any way to fix those cards? or even recover the photos on them?

You can try testdisk/photorec, that is assuming your N900 or Ubuntu can at least see the card and is just not able to mount them (check the output of dmesg after plugging the card).

http://www.sdcard.org/consumers/formatter/eula/

Use that program (you'll have to use Win I think). It always worked for me. Always.

with dmesg i get:
8.067749] mmc0: error -110 whilst initialising SD card

sd doesn't show up in file manager on N900.
i tried the SDformatter 3.0 but it does not find any removable media

Is that in your N900 and Ubuntu? I'm not sure, but with that error you probably won't be able to do anything, the only thing I can suggest is to make sure the contacts are clean and to try different micro sd readers.

On N900 that is.
solved the mystery with the 4gb card by putting it in freezer for half an hour and quickly inserting it to N900 and plugged N900 to pc (storage mode) and got all files rescued haven't tried it (yet) on 16gb card.

EDIT: freezer-trick didn't work for the 16gb card. maybe i have to buy a new one. 32gb maybe..

I am not a guru, but you could try partition the card with disk utility on Ubuntu (of course only if disk utility finds it). I managed to 'broke' my usb-pendrives using unetbootn and dd. That method saved them. Just a thought.

Error -110 smells like Kingston

hmm, maybe it is physical damage to the card. my GF told that she had the 16gb card in her 5800 and she dopped it and then took the card out... i can't see any cracks or anything on it though...

i have to try if ubuntu disk utility can detecd it...

it might look silly, but did you close the back part of the phone? if you don`t close,
not even if you find a golden Pegasus micro sd will work...