Button not responsive the second time

Question

I'm new to COM interopability so I'm sure this question may be an one easy one for you all. I've created an office excel addin to suit my needs; to be specific, i created a new floating command bar, and populated a couple of buttons into it. it works just fine, at first impression. then i realised that the buttons are no longer responsive after a few clicks. nothing happens when i click those buttons. the methods associated with those buttons are simply static class, that make the text lower cased, UPPER CASED, etc. any idea why this happens? i never encountered this when using VBE previously. THANK YOU in advance