[R] aov() question

[Leigh E Alexander]

Hi all,
So I think I have seen some similar questions to mine when I searched  
the archives, but have not seen any concrete answers and was  
wondering if any one could help.
I have been trying to use R's aov() function to analyze my data.  I  
have a 3 x 4 x 2 repeated measures design.  All of the IVs are within  
subjects.    I do also have missing values (unequal N), as I have to  
remove any incorrect trials for each subject.

Here is the code I entered and the error message:

a<-aov(log(rt)~(tran*block*half) + Error (sid/ (tran*block*half)),  
data=mydata2)

Warning message:
Error() model is singular in: aov(log(rt) ~ (tran * block * half) +  
Error(sid/(tran * block *

I then do summary(a) and am able to get an output, but I am not sure  
whether or not I can trust that output since I got the error message.
Any body have any thoughts/solutions for this?

Also, are there any benefits of you aov() vs. use some of the linear  
model functions or vice versa?

Thanks for any help you can offer!!

~Leigh Alexander