I tried to duplicate this with Fireworks CS4 to see if I could find a solution for you.
What I did was typed some text onto a blank frame in Fw to see what was available for styles.
Without doing anything additional I had 0 styles available in the properties of the text and no immediately visible styles in the Styles picker under "Current Document".
However, there were still the adobe provided styles in the Styles picker if I changed it from "Current Document" to one of the built in style libraries and once a style was selected from there it was imported into the current document list and added to the style dropdown for the text properties as well.
My thought here, and I'm only guessing at this stage, is that you may need to either import a custom style library or you may have somehow damaged your adobe provided style libraries and may need to re-install them. Either that, or you just have no styles previously used in your document and need to import them.
Otherwise I'm not seeing any reason why Fw would refuse to allow a style modification to text based on what the CS4 version does for me (again, I'm not using same version as you I don't think).
In CS4 Ctrl-F11 opens the styles window where you can select from the pre-built styles or import new libraries so dunno if that'll help for you or not.
Hope this helps :)
Edit: Wow, I had no idea how incoherent that reply was until I re-read it but I still hope it helps lol
