Cornix, thank you for the suggestion! Invokelater was exactly what I needed here. Below is my corrected code, now working correctly. This is a really good trick to remember...
private void addProcGuideWithValues(String base, String proc) {
procTableModel.addRow(new Object[]{base, proc}); // adding object to the table's table model
// perform this action later, once the scroll object is properly updated
SwingUtilities.invokeLater(new Runnable() {
public void run() {
JScrollBar bar = sclProcGuide.getVerticalScrollBar();
bar.setValue (bar.getMaximum() + bar.getBlockIncrement());
}
});
}