Hello, as well as the split screen problem I also had a problem with my e-mail account. the thunderbolt symbol kept appearing.
To cut a long story short this is what I have done.
I reset my router and the thunderbolts disappeared. The split screen problem was still there. I went into system prefs and clicked the user accounts. In the log in items section was this 'SpeechSynthesisServer' application. I removed it from the log in items, restarted the iMac and the split screen is now working and the e-mails seem to be OK. Any idea what 'SpeechSynthesisServer' application is? have I been hacked?
Thanks for your help.
Roger