Over in the Upgrade forum Jozef Aerts has asked for clarification on versions 1.5.4 and 1.5.5. As he rightly points out, the 1.5.4 builds of formsPlayer Community Edition are newer than the 1.5.5 ones, which is a problem if you have installed any 1.5.5 builds--you can't upgrade to the newer software, because the version number you are trying to install is lower.
The problem stems from not having made clear in the past which builds are 'previews' (only recommended for brave developers wanting to have a look at new features that are coming down the line) and which builds are part of the main development path.
We've been working for a while on making future developer previews completely
separate, to avoid confusion, and whilst we finish this process we've put on
hold the new features from 1.5.5 (custom controls based on
select1 will be easier to create). This means that for 1.5.6 we'll be
concentrating on finishing the last few items from XForms 1.1, and resolving
any outstanding bugs.
For further information see the formsPlayer Community Edition 1.5 roadmap.