Well, it was my bad, dreadfully sorry guys. My bad with the password and seed, mixed some things up :( Everything restored successfully.
I use Electrum 1.8.1 (portable edition) and have some mBTCs in my wallet (electrum.dat). I tried to send a payment and was asked to type the password which I had set before. The password is kept in KeePass, I pasted it from KeePass and... "invalid password". But it is correct for sure.
I have the seed (12 words) well kept. I tried to restore the wallet with the seed, after backuping my electrum.dat and deleting it, but if I paste the seed words and the wallet is created and synchronized, I'm told the wallet has no transaction history (therefore, no money there).
1) How could it happen that Electrum says the password is invalid when trying to send the money?
2) How could it happen that no transaction history is detected after using the seed (12 words) to restore the wallet?
3) Does it have anything to do with the list of Electrum servers? It is shown when I try to restore the wallet using the seed. If yes, do I have to try every server from the list to understand which one keeps the data about my wallet?
4) How do I recover my mBTCs from the Electrum wallet? I see the number I have, but can't send because of the password issue.
The first experience with Bitcoins and kind of frustrating... I hope I've explained the situation more or less well.