Northern blot trouble

[Fredrik Kamme]

Hi folks,
I've got a northern blot problem that goes like this:
I'm storing total RNA + 2vol eth at -20°, which I then ppt and run
formaldehyde gels, that look pretty nice. Everything has worked nice so
far, but now when I hybridize with cDNA probes or oligos, I get a fat
spot on my autoradiograms just at the well. Why? Is this RNA that never
dissolved? No obvious ppt's in my load sol's and nothing obvious when I
stain the gel with eth. bromide. The protocol has worked previously, but
now it doesn't. Is there a ppt formed over time when RNA is stored like
this, that is more difficult to dissove? I'm flabbergasted...:-(

Thanks for any help, a bewildered Freddy