RNA electrophoresis help

[John Frank]

i recently ran a RNA agarose electrophoresis (in denaturant conditions/formaldehyde) with ethidium bromide in the gel. since not even the markers were visible under the UV, i was wondering if anyone is aware of any possible interactions of the MOPS/formaldehyde/formamide mixture with the ethidium bromide (i am asking this because after seeing some protocols describing this procedure, i noticed people tend to stain with EtBr afterwards, as opposed to including it in the gel). thanks in advance :)

 - john frank