[BioC] getBM (biomaRt) sometimes returns NULL

[Giovanni Coppola]

Hello everybody,
I am using biomaRt to retrieve worm annotation.
Sometimes (apparently unpredictably) I get a NULL output and a warning:

 > getBM (attributes=c 
("wormbase_gene","go_description"),filter="wormbase_gene",values=wormids 
,mart=mart)->gobiomart
Warning message:
getBM returns NULL. in: getBM(attributes = c("wormbase_gene",  
"go_description"), filter = "wormbase_gene",

The exact same line works later. Has anyone experienced this? Is  
there a timeout issue or something like that?

Thanks
Giovanni


 > sessionInfo()
R version 2.2.1, 2005-12-20, powerpc-apple-darwin7.9.0

attached base packages:
[1] "tools"     "methods"   "stats"     "graphics"  "grDevices" "utils"
[7] "datasets"  "base"

other attached packages:
biomaRt    RCurl      XML  convert   marray    limma  Biobase
"1.5.12"  "0.6-0" "0.99-6"  "1.4.0"  "1.8.0"  "2.4.7"  "1.8.0"