[mythtvnz] Partial Sat lock several days following heavy rain

[Tortise]

Hi
Anyone come across this here?  I checked the Coax cable resistance when it was a problem (LNB disconnected) and got infinity with 
good digital Multimeter suggesting to me there was no water in the coax.
The flickering partial lock (un-viewable) has gone again and is OK but I expect heavy rain will make it return.
Is this likely to be water in the LNB itself?
Its an oldish Sharp 11.3Ghz
Perhaps it should be replaced?
Any experience or suggestions appreciated here.