Since the item flagged appears to relate to a hidden script (i-frame) it has probably detected an infection in a web page you were navigating to and blocked it.
If this is the case, no further action is required, except to inform the site operator that the site has been hacked.
If this appeared as a result of a scan, however, rather than on-access, different story.
What was the message displayed by Gdata?
(G-data uses two AV engines, hence the "a" and "b" references.)