[R] Putting referenced titles on plots

[grr@grell.mailshell.com]

I have a data frame "ctx" and an array "names", where names[i] is the 
column name for ctx[i], and am making histograms for each column of 
ctx:

for (i in 2:ncol(ctx)){hist(ctx[,i], br=100, main=names[i])}

The titles don't come out like I expect. Each names[i] is something 
like "1098_s_at" and R doesn't seem to like printing these. Instead, it 
prints "1" or "2" or "3" etc.

I have also tried binding ctx and names into a single data frame and 
referencing the first row of each [i] as the title, but I get the same 
result.

Can someone tell me how to get these titles attached?

Thanks,

Graham