I suggest trying a new wallet client
But i can't insert the private key I extracted from the multibit client, can I?
I thought you did it before.
There is a menu with import and export of private keys. After a new installation simply use this to import the previously exported keys.
Ok so this is not client dependant?
Private keys are client-independent. As noted in my previous post, you can import them into a different local wallet client, or into an online wallet. The process varies, but there's always (so far as I've seen) a way to do it.
Attention, Hem4Tic1 is a newcomer. The exported file IS client dependent. The key itself is not. Go on with multibit and the exported keys.
and what about the blockchain.info wallet? Can I make a wallet there, import the key i got from my multibit client and have the btc show up there? that seems like an easy way to solve the problem..
This would require a plain text export also. Kneim's got the right idea: if we can get MultiBit to do its job, that's probably going to be the smoothest solution for you.
Ok seems valid. But I am not really sure what to do now. Should I 1. find the .wallet file and back that up 2. delete all the other multibit files 3. install multibit again 4. import private key?
Here are the steps I'd use. It's a longer process, but it's one way to be absolutely certain that your old .wallet file isn't messing things up:
1. Find the .wallet file.
2. Make a copy of it and the whole folder it's in. This is sort of overkill, but better safe than sorry, right?
3. Uninstall MultiBit through the Add/Remove Programs control panel. Check the "force the deletion of..." checkbox.
4. Reboot.
5. Go back to your original .wallet file's location. Rename that file, or better yet, rename the folder it's in.
6. Reinstall MultiBit.
7. Import your private key.
This ensures that your old .wallet file can't cause any issues with your new MultiBit install.
If you'd like more in-depth help finding your .wallet file, let me know. I know how frustrating it can be to bang your head against XP.