Problems with writing ( in eclipse?-Collection of common programming errors

Keyboard shortcut mistakenly defined? Or other config problem. Have you been changing keyboard shortcuts recently? I’d expect that with a fresh install of Eclipse, the ( bracket key will work fine.

Another possibility is that some badly-written content-type editor is parsing & crashing on the (.. could be possible, though Eclipse isn’t generally structured this way. Try closing the file/resource and opening it as “text”.

Or, as @Lasse_Christiansen says — accidental input-language change.