I'm using QGIS 2.16 but this was happening on 2.14 as well and I hoped updating would fix it but no.
I create a new shapefile, doesn't matter whether it's a point, line or polygon, toggle edit function, and then use the edit add feature function to add a feature to the new shapefile. When right-clicking to finish my new feature the feature attributes window pops up but it is blank and I can't edit the attribute which means I can't add the feature. See the image.
I suspect there is a conflict with some other software on my computer or a previous version hasn't been removed completely because I have been having trouble with browsers and videos as well. I have tried using the tools of CCleaner to tidy up my registry and redundant files. I tried updating from 2.14 to 2.16 and I have tried removing 2.16 cleaning everything and reinstalling 2.16 but the problem still exists. Can anybody offer some advice of what else to try?
Note the other edit tools work such as copy, paste, move and node tool and my work around is to copy and paste a feature then reshape with node tool or move it but this is slow. None of the add... tools work.