Hello,
after an update from opensuse-11.4 to 12.3 I had a wallet named 'kdewallet'
in my kde-wallet-manager which I never (knowingly) introduced and which
kept me asking about a wallet-password I don't know.
So I just deleted that 'kdewallet' and made a new one named 'Default' which I
now use for storing my kmail-passwords (a pita story by its one).
But after a while (and some reboots) I again see a 'kdewallet' which asks
for a password I never gave to it (blank and/or system password does not work).

So, is this a bug or what is the 'kdewallet' meant for ?
If its a standard-system-wallet I should not delete - so what is the password for this ?

I'm not sure why this is happening. To fix this, try opening System Settings > Account Details > KDE Wallet, and make sure the wallet you created is selected for the "Default wallet". Once this is done, you can delete the automatically created "kdewallet". I've no idea what the password on it could be - KDE should not be creating a wallet by default.

Thanks for the help - I've probably found the reason/solution:
On my home there was still an old ~/.kde-Tree in parallel to the new ~/.kde4
from an older (somehow broken) KDE-Installation. Now every time I started
my fresh KDE-4.10 the kwallet tried to merge my old+new installation without
cleaning the old stuff. Hence deleting only worked in ~/.kde4 and the next
re-login started the merge of ~/kde & ~/.kde4 again.

Is this a general issue - i.e. is it save/recommended to just remove ~/.kde
(and if so - why didn't the kde4-update merge & remove the old stuff?) ?

Interesting, migrations of configurations are only supposed to happen once. That is quite unusual that it would happen multiple times.
I suspect the old data was not removed to allow for a return to the previous configuration if the migration failed (or to allow for a migration by hand).

In this instance, removing the old data was the correct course of action.