so, i managed to reimport the addresses containing coins into a new electrum wallet.
however i still have the same problem with them. "not enough funds" when trying to send any amount of coins.
Actually, the workaround I had in mind is to import those addresses into another client (such as bitcoin-qt, multibit, or blockchain.info), and spend the coins from there (even sending them back into a new electrum address should fix it, I guess)