Can't find any solution yet. Ubuntu starts booting and halts in several seconds. When boot in save mode, the console shows uncorrectable disk error. I can boot from live CD and observe all my disk content. Is any way to repair without reinstall? If reinstall is required, then what's the best way to transfer data? Live CD seems hasving not SSH for security reason.

Another question, I have added a disk for swap, how can I make it using Ubuntu?

You need to back the data up regardless. I tend to use an external disk, but you should be able to use ssh - I just tried a Knoppix liveCD, and it merely needed to be started. I was able to ssh out to my test server. As root as it happens, so everything should be available to you.

After backing it up, you could try a fsck on the broken system - be aware that if you do "fix" things with fsck, sometimes they can be broken (truncated files, or invalid inodes in the chain for example).

Adding a swap is as simple as "mkswap /dev/<whatever>" followed by "swapon /dev/<whatever>".
Update fstab to make it permanent.

Thanks. I am going to use a flash drive for backup. Is there any way to repair broken files. For example fsck removed unreadable blocks from files making them corrupted. Some tool which can compare original Ubuntu system files and files on disk to find corrupted and replace with good ones? Reinstalling Ubuntu isn't big deal, I am just looking for a faster solution.

Re-install will be fastest.
I'd suggest you save the entire /home/* Then pre-partition the disk prior to reinstall, and restore the /home into a separate partition.
Then re-install using that /home, and use the same userid/password when prompted. Everything should "just work" - I occasionally have to roll-back Ubuntu like this when I'm testing new alpha/beta releases.
See this similar discussion.