My K800i was just on the table and when I picked it up to set my alarmclock I noticed that the screen was collored like a negative photo.
So I shut it off and turned it on again.
Then I only got a blurry screen. You can not make out any thing, but the phone seems to be working.
A few months ago I unlocked it from Dutch KPN provider, because I am now living in Egypt. It has been working fine since February.

How can I save my K800i?

Try reflashing it.

http://forums.se-nse.net/index.php?showtopic=23459

Hamdullah (thank God in Arabic), the phone is working again after I removed battery and sim-card for a whole night.

But when I now but back my Egyptian sim-card (Mobinil) the phone asks me to put in the correct sim-card for the phone. And when I put in the old Dutch sim-card (KPN-HI, the one it was locked to before) it works correct. So the simlock is back on the phone.

From which step of the tutorial steadyontherem8 posted in this topic I should start with "unlocking" my phone, so I can use my Egyptian sim-card again?

Two remarks after reading the tutorial:
I do not want the K810 firmware, which steps should I skip?
Could some one walk me through all the way? :-$ Because I do not get which firmware and custom pack I am going to need :-$

Try going to topsony.com, click languages description on the left bar. Scroll down until you find K800 and choose which fs you want and post it here.

Unlocking phone: http://forums.se-nse.net/index.php?showtopic=20668

I checked topsony.com and I need/want Europe_3.
The big problem is now, that when I try to register my whole Viste computer goes crazy. So if anybody could post a link to the Firmware I need.

This is what setool2lt says when I click read flash:
ChipID:9900,EMP protocol:0301
PHONE IS RED RETAIL PRODUCT
FLASH CID detected:53
Speed:921600
OTP LOCKED:1 CID:51 PAF:1 IMEI:xxx CERT:RED
FLASH CID:53 COLOR:RED
Can't build loaders chain ;(
Elapsed:0 secs.

Thank you very much for saving my life ;-)

You need to use jdflasher because your phone is CID53.

AFAIK JDflasher can't patch CID53.

So this means I can not "unlock" my K800i? :-(

Not for free. You need to go to an unlock shop or ask your operator for a code.