I installed the Slideshow Gallery 2 plugin by Cameron Preston & Antonie Potgieter. It appeared to work just fine, but the TinyMCE editing buttons disappeared from the 'Edit Page' screen for all posts, pages, etc.
Also, all of the content within the text box editing area became invisible. I could still select it, and see there was something there, but the images were not visible, and the text was white, which blended with the background.
Interestingly, I only had this issue in Chrome, Firefox & Safari, but not in IE (internet explorer). I deactivated all of my plugins, and that's how I found out this one was causing the issue.
Just thought this would be helpful info if it happens to someone else.
If you're curious, I went with the Nivo Slider for WordPress plugin instead. It's pretty basic, but comparable to the Slideshow Gallery 2 plugin. (Nivo plugin)