[BioC] Affy : checkSlotAssignment() Error

[Sundaram, Shyam (NIH/CIT)]

Hi:
Thanks in advance for helping.
I was able to load successfully the "HG-U133A" CEL and CDF file through the
ReadAffy() method into a "plob" object. When I tried to convert it to the
exprSet using the express() function I was faced with the following error
message.
Normalizing Data
Error in checkSlotAssignment(object, name, value) : 
        Value supplied is not valid for slot "pm", is(value, "matrix") is
not TRUE
To make sure the cel,cdf files are loaded properly I tried to load them
through the read.celfile, read.cdffile methods and they seem to do so with
out errors.
Any suggestions on what might be the cause of the problem?