Having the same problem with 1.9.8. My online wallet is on Windows 7, while offline wallet is on Ubuntu. Just lately when I try to take a transaction to the offline wallet and sign it the program hangs and refuses to sign. Can someone point me in the best direction to fix without reinstalling? Thanks!
What is the version you're using on your online computer?
Also, what are the specs of your offline computer? How many inputs does the transaction you're trying to sign have?
If your online wallet is >=2.0 (aka Github version) then you can not sign transactions using any pre-2.0 version.
If you are using 1.9.8 on your online, then it might be due to too many inputs + low specs on your offline wallet.
I had a reeeeally crappy mini-notebook I was using for offline signing, and when I signed a transaction with 15 inputs, it would freeze for 5 minutes, then the signed transaction would finish.
If it's "hanging" I would recommend just waiting it out... Maybe try signing it, then let it hang for like 30 minutes while you're doing something else, and see if it actually finishes.
Online and offline are both 1.9.8. I just reinstalled the offline 1.9.8 and tried a small .1 btc send, went ok. Next tried a larger transaction of one bitcoin and the transaction signs on the offline computer but clicking on the save button does nothing. I can not save the signed transaction to the usb key. This is a real problem for me. Program has been trouble free up to now. Ubuntu 12.04 lts on an older Toshiba laptop.