Do you have a screenshot for this?
This sounds very unusual, and I can't think of a reason why it would occur. What's especially odd is that you say that functions are grayed out, and yet half of those grayed out functions work! (Typically a grayed out function cannot be interacted with in any way.)
A text object would be uneditable if it were locked within the Layers panel, or if it had been converted to paths (using Text > Convert to Paths). Other than that, I can't think of an explanation.
Is this happening within a single document only? Or across multiple documents?
Yes it is unusual. If it was just grayed out and didn't work, it would still be a problem. The fact that it's grayed out but also works just makes it downright stranger.
It happened in one document for about 10 minutes. After I minimized the window and reopened it all the unfunctions became ungray and usable again.
So the problem is resolved for now. But I'll screenshot it in the future if it happens again.
What version of fireworks are you using ?
Try reinstalling fireworks or check on your fonts ( "there might be corrupted fonts") or try disabling some extensions