[BioC] Problem loading saved GenomicRanges object

[Michael Dondrup]

Hi,
I have saved a GRanges object and now after updating GenomicRanges I have trouble loading it again:

> gr
GRanges with 2581 ranges and 4 elementMetadata values
Error in validObject(.Object) : 
  invalid class "GRanges" object: slots in class definition but not in object: "seqinfo"
> 

This data is very important, so is there a way to restore this object?

Thank you for your help.
Michael 

> sessionInfo()
R version 2.12.1 (2010-12-16)
Platform: x86_64-apple-darwin9.8.0/x86_64 (64-bit)

locale:
[1] en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8

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

other attached packages:
[1] GenomicRanges_1.2.0 IRanges_1.8.9      
>