Just in case. To make my description more clear.
I successfuly signed the transaction by my old offline Electrum 1.9.8 wallet, but this transaction isn't accepted by Electrum servers (I suppose), blockchain.info also rejects it saying something like "noncanonical signature, high S", something like that.
The address from which I wanted to spend is 13'th in the list of receive addresses of online client, predictably I don't see it among the first 5 addresses which offline client shows. And now there is no 'sign' button when I load the transaction from file in the offline client.
Edit. More details, may be they are important. In order to upgrade the offline client, first I tryed to run the setup script: 'sudo python setup.py install', but it exited with an error. Then I just launched the client with 'python electrum', it launched OK, but I got the described problem.
Edit 2. Is there a way to see more receive addresses in the offline client? If they continue to be different from the online client, then probably different clients generate different keypairs from the same seed.
Do not worry about the addresses in the offline client...
Create the TX with a watch online 2.5.4 client. The sign with the 2.5.4 offline client.
Just download the 2.5.4 tarball and extract the tarball then run ./electrum from the directory. No need to install anything...