Is there any way that I can make the suggestions box wider without actually changing the width of that jtable column? I want to make the suggestion box wider than the actual jcombobox.
The standard way is to use the JComboBox.setPrototypeDisplayValue() method; ideally you'd pass in the longest item so that the combobox can set a good default width.
This is briefly touched upon in the GlazedLists Developer Tutorials; see "AutoCompleteSupport Screencast" for the walkthrough.