Pocket edition: "My World" can't be opened

I just bought Minecraft PE for my tablet - but I am unable to create local maps and play Minecraft.

I just installed Minecraft and clicked "Play" -> "New" -> "Create World!" and get the message >"My World" can't be opened< (see attachment).
The new "My World" map is not listed in Minecraft after the error.

But the map is created under /mnt/sdcard/games/com.mojang/minecraftWorlds/My World with the following files:
/db/current: contains the text "MANIFEST-000001"
/db/LOCK (empty file)
/db/LOG contains the text:
2014/12/30-16:01:48.979186 54d9f348 Log #3: 0 ops saved to Table #4 OK
2014/12/30-16:01:48.995517 54d9f348 Archiving /mnt/sdcard/games/com.mojang/minecraftWorlds/My World/db/000003.log: OK
2014/12/30-16:01:49.000046 54d9f348 Archiving /mnt/sdcard/games/com.mojang/minecraftWorlds/My World/db/MANIFEST-000001: OK
2014/12/30-16:01:49.014881 54d9f348 **** Repaired leveldb /mnt/sdcard/games/com.mojang/minecraftWorlds/My World/db; recovered 0 files; 0 bytes. Some data may have been lost. ****
/db/LOG.old contains the text:
2014/12/30-16:01:48.971949 54d9f348 MANIFEST write: IO error: /mnt/sdcard/games/com.mojang/minecraftWorlds/My World/db: Bad file number
/db/MANIFEST-000001 contains the text (looks like a binary file):
5cgŽ"� leveldb.BytewiseComparator

• I have tried rebooting the tablet
• I have tried re-installing Minecraft
• I have tried deleting the folder /mnt/sdcard/games (with contents)
• The SD card has 8.43 Gb free space
• The game runs fine when joining another server on LAN