Has something changed between Windows 7 64 bit and Windows 8.1 64 bit with respect to installing the Workbench to avoid the "An internal error occurred during: "FrontEnd Job::Open Notebook" issue?
Just tried Rolf Mertig's fix, which may have worked on some systems before. However, I downloaded Eclipse Kepler then attempted to add Indigo via http://download.eclipse.org/releases.indigo as suggested, but received an org.eclipse.equinox.p2.core.ProvisionException: "Unable to read repository at http://download.eclipse.org/releases/indigo" as suggested in Rolf Mertig's fix, which was regarded as a solution to this problem. Although this issue has reappeared subsequently without further comment (regarded as duplicate issue for a Windows 7 64 bit installation), its not clear to me that the latest "Answer" (dated 9 July 2013) is still applicable..
I've tried various combinations of downloads of both java and eclipse, but am unable to get Workbench to play nice with any of them. They seem to work fine for other purposes.
It is surprising that despite internal use of Workbench at Wolfram and much subsequent development of Eclipse, this evidently is still and issue despite assertions to the contrary. Workbench 2.0 seems to be long in the tooth, no?