As per a multitude of threads, Cubase (and some other hosts) have trouble passing on text to plugins.
Etc etc. This is a VERY old problem (as it exists since Cubase 3.x!) which never seems to have been addressed. I’m currently testing with Cubase 7, and the problem still persists - this doesn’t look like it’s getting solved any time soon on the side of Steinberg.
A few fixes were proposed which mainly fall into two important categories: either patching the vst wrapper to support keystrokes coming from the host (which yields incomplete results as keys like “.” seem to not get through - but it is still a nice first partial fix) or alternatively making TextEditor fields modal/addToDesktop. It would be Really Nice if either/both of these things could be integrated into Juce, especially as special things need to be done to any editable Label too (as it creates a TextField). All of the old threads have been abandoned and/or closed by Jules for unknown reasons… Both fixes could be added without breaking other things.
For us TextFields are really important as the activation of the plugin is done from within the plugin and all of our parameter display labels are editable.