[BioC] cummerbund Error in Volcanoplot

[him]

Hi, I have a question about cummeRbund package.
I upgraded my R and cummeRbund to 2.15 and 1.2 respectively.
ever since when I run the following commend I get an error.

> cufdat2b=readCufflinks('diff_out_2b/')
> csVolcano(genes(cufdat2b),'C','P')
Error in eval(expr, envir, enclos) : object 'log2_fold_change' not found

other plots work find. what could I do to fix this?
Thank you.