I use a custom dashboard widget on my clients' sites (code here - that's not my snippet, but that's the same code.)
I noticed my custom widget wasn't showing up. After much hunting, I realized it's Twitter Widget Pro that is suppressing it. If I deactivate TWP, then my custom widget shows up.
Using Screen Options, I turned display of the big Xavisys dashboard widget off. When I turned it back on, my custom widget showed up.
Since TWP seems to be broken otherwise, I'll just try and find another way to add my Twitter feed.
