levelplot problems !!!

Dear R users,

I have changed my R version to the new 1.8.1 and some problems appears when 
using the previous levelplot code. 

This is a simple example:

a <-1:10
b <-11:20
j <- rnorm(100)
grid<-expand.grid(a = a, b = b)
levelplot(j~a*b, grid)

Normaly in my previous vs this was suffice to produce the levelplot.
Now, an empty  R graphics device appears with the following error message:

Error in grid.pack(frame = key.gf, row = 1, col = 1, grob = grid.rect(x 
=rep(0.5,  :        unused argument(s) (frame ...)

Are there any solution?
Thanks in advance
H

.........................................................
Hernan J. Dopazo
Bioinformatica. CNIO 
c/ Melchor Fern?ndez Almagro 3 
28029, Madrid, Espa?a 
Tfn: (34) 91 224 69 00 ext: 2428 
Fax: (34) 91 224 69 23 
http://bioinfo.cnio.es 
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