It looks like a corruption in the native heap while Eclipse is running. (The mention of "malloc" is the clue ...)
AFAIK, there is no easy answer ... unless you can track down similar problem reports. Without that, it is not possible to say what specifically is causing this, but the most likely explanation is some bug in one of the native libraries that Eclipse is using.
I'd recommend the following:
See if the normal restart / reinitialization tricks make any difference.
Install a fresh copy of Juno release 2, adding your plugins and seeing if that makes any difference.
Try again, but this time with as few plugins as you can bear.
If at any point you are confident that you have scenario that allows you to reproduce the problem AND reproduce the Eclipse setup, submit a bug report.
One should not entirely discount the possibility that you've installed a corrupted Eclipse download, something has corrupted your copy on disc or you have a hardware fault (a bad memory chip, flaky CPU, etc)