top vertical alignment of table content

[Heinz-Uwe Hobohm]

Lyx 1.3.3 on Mac-OSX 10.3  produced this piece of tex code where table  
field contents have been asked to align TOP VERTICAL, however,
after running pdflatex on this code the left three text columns align  
below the picture.

How I make align the first three column contents "top vertical" ?

Kind regards
Uwe


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% LyX specific LaTeX commands.
%% Because html converters don't know tabularnewline
\providecommand{\tabularnewline}{\\}
\usepackage{babel}
\makeatother
\begin{document}
%
\begin{table}
\begin{longtable}{|>{\raggedright}p{2cm}|>{\raggedright}p{1.5cm}|>{\ragg 
edright}p{1.5cm}|>{\raggedright}p{2cm}|>{\raggedright}p{6.2cm}|}
\hline
Chip type&
Organism,

sample tissue&
probe localization, chip size {[}probes{]}&
Background range (black:lowest, yellow: highest)&
Background image\tabularnewline
\hline
Hu35KSubB&
Human, macro-phages&
probes adjacent, 532x532&
1246-2138&
\rule{5.5cm}{5.5cm}
\tabularnewline
\hline
RG\_U34A&
Rat,
hypothala-mus&
probes distributed, 532x532&
333-426&
\rule{5.5cm}{5.5cm}
\tabularnewline
\hline
HG-U133A&
Human,
macro-phages&
probes distributed, 710x710&
91-150&
\tabularnewline
\hline
\end{longtable}
\caption{Background calculated for each probe as the average of lowest  
3\%
signals of a 30x30 surroundig square and visualized as colour scale.
Colours range from black (lowest background) to yellow (highest  
background).
Note that colour scales differ for different chip types (column four).
White spots indicate areas without probes or probes without  
annotation.\label{table:Background-images}}
\end{table}

\end{document}