thats unsualy for the frequency to break up on a 1.8m dish.
does this happen on any other channels / frequencies or just that one?
maybe your dish had blown out of alignment due to the recent winds we have had?
maybe your cable connections are loose?
i never use invertos as i dont rate them at all - some installers use them as they are cheaper than invacom prime focus LNBs....but i fond that invacoms perform much better than the invertos i have seewn being used (i have replace many invertos installed in my area and noticed a vast improvments in signal / reception times!)