Boxplot is supposed to show you the following values:
Median, 25th and 75th percentile and outliers if any exists.
I think you should investigate the numbers in your data and see if they are all proper numbers.
You can also break the vector into pieces and make a boxplot of the pieces to see where the problem is coming from.
For example:
uu_FirstPart=uu(1:100000);
uu_SecondPart=uu(100001:250000);
boxplot(uu_FirstPart);
boxplot(uu_SecondPart);
% You could break it into 10 parts if you want.
% You just need to investigate your data first and be sure that the values are reasonable
