Yesterday, on my way home to Jogja from Jakarta, my Nokia 5800 didn’t work at all. Last time I checked before boarding — it was in Soekarno Hatta airport — it worked without any issue. I just switched to “Offline” mode. Few minutes after that, I only had blank white screen with the Nokia logo. Something was wrong, and I decided to switch off my phone. I waited after I touched Jogjakarta.
When I was in the airport in Jogjakarta, I tried to switch it on hoping that it’s back to normal. It gave me the same error. Nothing I could do. Damn! When I got home, I tried to find the solution, and I used these solutions.

Your memory card is corrupted.
Firstly hard reset your device without inserting the memory card. And after hard resetting just insert back your memory card.
If still the problem persits just attach your device to your PC in Mass Storage mode and right click your memorycard and select properties and select tools and select check now..i.e. scan disk your memory card for errors… (source)

This is what I did:

• Switch off the phone and pull out the memory card.
• Switch on the phone without memory card. It’s back to normal now.
• Switch it off again and insert its memory card back, and turn it off.
• It’s working again.

I was worried that the only solution was formatting my memory card. At least, next time I get this kind of problem, I should know what I must try. Is there any other solution to solve this kind of error?