Recenty I used Inkscape 0.46 on Mandriva 2008.1 and there was no problem about fill-opacity.
I changed to 2009.1 still using version 0.46 and the following error occured:
I cannot set colors more from value 245!!!
Example:
I want full white with R=255, G=255, B=255 but there's a limit on the slider with value 245.
I opened the XML editor. I saw the following settings:
opacity:1;fill:#f5f562;fill-opacity:0.96078432
instead of
opacity:1;fill:#f5f562;fill-opacity:1

When I delete the value (opacity:1;fill:#f5f562) goes right.
But when I create a new rectangle the opacity limit is on.

I think this error come with bad compiling of Inkscape to Mandriva 2009.1.
What do I have to do to solve the problem?
Inkscape cannot be complied on this machine by me.
The older port (v0.46 to 2008.1) is not running on this new 2009.1.

Bug #257685 in inkscape (Ubuntu): “Inkscape color chooser widget's maximum limited to 245 instead of 255”:

Gez on 2009-04-25 wrote:it's fixed in SVN. The fix will be included in Inkscape 0.47, (…) Meanwhile, you can try a development version

hth, ~suv