! You can't use `\prevdepth' in horizontal mode.

Dear users,

I ran into problem with a number of floats I have in my document. I had 
to change the figure placement from [ht] to [H] because I place a number 
of floats after eachother with no text in between. The float package is 
recommended. But I run into weird error -- ! You can't use `\prevdepth' 
in horizontal mode --. I only occurs with one picture. With the others 
the switch to the [H] specifier works fine. I'm not an expert users, but 
is there a solution to this problem?

Thanks in advance,

Wilfred

Part of the log file:

Underfull \vbox (badness 10000) has occurred while \output is active 
[1964 <c:/Users/wilfred/Documents/tex-documenten/picture4.pdf>]
! You can't use `\prevdepth' in horizontal mode.
\nointerlineskip ->\prevdepth
                               -\@m \p@
l.29601 \end{center}

! Missing $ inserted.
<inserted text>
                 $
l.29601 \end{center}

! Missing number, treated as zero.
<to be read again>
                    \hbox
l.29601 \end{center}

! Illegal unit of measure (pt inserted).
<to be read again>
                    \hbox
l.29601 \end{center}

! Missing $ inserted.
<inserted text>
                 $
l.29601 \end{center}


! LaTeX Error: Something's wrong--perhaps a missing \item.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
  ...

l.29601 \end{center}

[1965 <c:/Users/wilfred/Documents/tex-documenten/picture5.pdf>]

! LaTeX Error: Something's wrong--perhaps a missing \item.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
  ...

l.29601 \end{center}


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