This Bugzilla instance is a read-only archive of historic NetBeans bug reports. To report a bug in NetBeans please follow the project's instructions for reporting issues.
It is possible to add more than one breakpoint on the same line (Java source code) with Ctrl+8, in particular when the machine is under heavy load. The first time this happened to me was accidentally, but I can reliably reproduce it by starting some CPU-intensive task (outside of NetBeans) and then holding Ctrl+F8 pressed, so that Ctrl+F8 is triggered multiple times per second through key repeat. (I'm using a Pentium 4 with hyper-threading by the way.) The result is that the breakpoint icon changes to a double box, and its context menu says "Multiple Breakpoints". The problem now is that there appears to be no way to remove this multiple breakpoint. The Breakpoints window only shows one entry, which can be toogled with Ctrl+F8, but the icon and highlighting in the editor remains, even after closing and reopening the source file. It seems that there is a race condition in Toggle Line Breakpoint that creates unexpected internal breakpoint structures.
Created attachment 89021 [details] Screenshot of multiple breakpoint on the same line.
This should be already fixed by http://hg.netbeans.org/main/rev/d6ddb07ee672 (See also issue #173700). Please verify after this propagates to a dev build. Thanks.
Try Deleting your Netbeans Project Folder and reload your project, it should clear the breakpoints out.