something odd with SSCP ? (or maybe it's just me ...)

Dear Praat users, Dear Paul

I am having a problem with the following lines (that I've been using for a long time though)
I intend to draw formant (F1 and F2) ellipses from data contained in the first 2 columns of a text file.

select 'table_temp'
To SSCP... 0 0 1 2
sscp = selected ("SSCP")
Draw confidence ellipse... 'niveau_confiance' 2 1 'en2$' 'en1$' 'enonces$' 'en3$' no

... and seems very odd to me ...
if the number of rows of the table is less than 46342, then everything is OK and I get my ellipse right
If it is more, then no ellipse appears at all
But then again, if the number of rows is more than 66000 (approximately this time), then it appears back.

In this last case, it seems that the confidence level gets smaller and smaller as the ellipse gets progressivel smaller.
But I progressiveley increased my data from 46341 to 46342 by artificially copying old data lines (thus not increasing standard deviation), and I could see the ellipse suddenly disappear.
Is there something I am doing wrong ?

Thanks for any hints ....

Laboratory of Phonetics and Phonology, Paris

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