[R] different results by re-ordering vector: bug?

[Carlos Soares]

Dear R users,

I obtain the following behavior which I cannot understand. Given a file 
mydata with the following numbers:
0.171409662475182
0.15817339510258108
0.32230311052283256
0.14890800794176043
0.17074784910655194
0.16611515552614162
0.41
0.16611515552614162
0.41760423560555926
0.11978821972203839

I read the data and perform some calculations:
a <- 1-read.table("mydata")$V1
m <- outer(a, a, "/")
diag(m) <- NA
mean.row <- apply(m, 1, mean, na.rm=TRUE)

which yield the same value for indices 6 and 8 of mean.row, as would be 
expected because values 6 and 8 of the original vector are the same:
 > mean.row[6]==mean.row[8]
[1] TRUE

However, if I reorder the values as follows:
a <- 1-read.table("mydata")$V1[c(10,2,8,9,7,3,1,4,5,6)]

and repeat the calculations:
m <- outer(a, a, "/")
diag(m) <- NA
mean.row <- apply(m, 1, mean, na.rm=TRUE)
mean.row[6]==mean.row[8]

The values for indices 10 and 3 of mean.row, which correspond to 6 and 8 
in the previous calculations, are not the same anymore:
 > mean.row[10]==mean.row[3]
[1] FALSE

I understand that limited precision causes "incorrect" results but I 
wouldn't expect ordering operations to do the same. I couldn't find any 
information in the site about this. Maybe it's a bug with my version:
 > R.version
         _               
platform i686-pc-linux-gnu
arch     i686            
os       linux-gnu       
system   i686, linux-gnu 
status                   
major    1               
minor    7.0             
year     2003            
month    04              
day      16              
language R               

Thanks and best regards,
Carlos