[BioC] limma background correction

[Henrique Proença]

Hi,

I am trying to analyze some quantarray files using limma Guide, when 
suddenly it gives me the following error at the background normalization 
step (using normexp method and offset = 50)

Error in if (all(abs(delta) < 1e-10)) break :
   missing value where TRUE/FALSE needed

I can't find why this happens.
Does anyone an idea of what is happening?

-- 
regards
Henrique Proença