According to Joystiq, the Czech ambassador was invited to a meeting by the Greek president related to jailed Bohemia Interactive employees Ivan Buchta and Martin Pezlar. The two have been charged with espionage and are being held without bail. They have been in jail since September of this year (75 days so far).
HelpIvanMartin.org has been closely following the case against Ivan Buchta and Martin Pezlar. They claim in this post that the meeting was set up in response to a letter from Czech President Vaclav Klaus urging Greek President Karolos Papoulias to give the case special attention.
You can get the blow-by-blow on the latest developments in the case by visiting www.helpivanmartin.org.