Jules, here´s a bug report. This doesn´t happen for the Juce Demo 64 bits, only with the Juce Audio Plugin VST Demo 64 bits and MSVC2013. (I don´t have any other compiler to test, sorry)
This also happens with the ToolTipWindow, so its something related to fonts or font-sizes? For the test below all I did was compile the Juce Audio Plugin VST Demo, did nothing but added an AlertWindow to test.
Well, in some cases you just can't avoid that, don't you think? For example, if you are overriding a preset or losing some saved changes when loading one, a modal dialog is what is required to ask the user for confirmation
If you really, really can't find a better way to handle it, then you must at least avoid running a modal loop, and instead show your component modally, and get the result asynchronously via a callback. Setting JUCE_MODAL_LOOPS_PERMITTED=0 will help prevent you messing up.
I'm not sure why this is going to be a problem.. Is it because it could blow up in case one closes the Host application while the modal window is being displayed?