Birte S. schrieb:
my problem is similar with lyx 1.6 and installed packages soul and xcolor and reconfiguration of lyx and restart of lyx, though the error message is as follows: " Changes will not be highlighted in LaTeX output when using pdflatex because xcolor and soul are not installed. Please install both packages...
So you need to install the LaTeX-packages "soul" and "xcolor". What is your operating system? On Windows, simply open MiKTeX's Settings (available via the Start menu). There set the option "install missing packages on the fly" to "yes" (probably this option is already set). Finally, open an Internet connection and reconfigure LyX. All LaTeX-packages needed by LyX will then be installed automatically.
In case you are on Linux, use the package manager of TeXLive to install the packages.