[R] start() in zoo

[Arshavir]

Hi,

I'm trying to get the beginning of my zoo object's index through start 
(d) but sometimes get an error:

Error in start(d):
        Unused argument (s)  (c(NA, 8.792, 8.725, ...)

The data(d) is retrieved from Bloomberg through RBloomberg. I am  
pulling 6 tickers (which means I'm getting 6 columns), and not all of  
them have data going back to my start date. When I print the object,  
there are no errors. And I do see the NA for some of the columns for  
the earlier dates. Also, this is daily data.

Any suggestions on what could be causing this and also what the error  
means would be greatly appreciated.