Sweave-output causes error-message in pdflatex

Dear list,
Latex/Sweave has trouble processing Sveave-output coming from the 
summary-command of a linear Model.
 >summary(lmRub)
The output line causing the trouble looks in R like this
Signif. codes: 0 ?***? 0.001 ?**? 0.01 ?*? 0.05 ?.? 0.1 ? ? 1

In my Sweaved Tex-file that line looks like this
Signif. codes: 0 ?***? 0.001 ?**? 0.01 ?*? 0.05 ?.? 0.1 ? ? 1? (actually 
in the editor the quotation signs are replaced by bars, but they got 
lost through copy & paste. I don't know if that says anything about my 
problem.)

In the error message produced through pdflatex, the quotation signs 
reappear.
Latex error-message:
! Package inputenc Error: Keyboard character used is undefined

(inputenc) in inputencoding `Latin1'.

See the inputenc package documentation for explanation.

Type H <return> for immediate help.

...

l.465 ...*? 0.001 ?**? 0.01 ?*? 0.05 ?.? 0.1 ? ? 1

You need to provide a definition with \DeclareInputText

or \DeclareInputMath before using this key.


I hope anybody knows how I can prevent that error message. Thanks in 
advance.

Gerrit