[Histonet] DAKO FISH pretreatment buffer (MES)

[Kim Merriam]

Hello,
This might seem to be a strange question, but I have been working up my FFPE FISH procedure with the DAKO FISH Histology Kit (I have had some nice preliminary results).  I have been noticing a strange greasy film on my slides that seems to be occuring during the heat pretreatment step (DAKO pretreatment buffer, which is MES; a very long name and a buffer I have not used until now); there is also a greasy film on the top of the buffer solution.
Is this common?  Can it hurt my slides?  I did manage to remove it by dehydrating my slides through 95, 100 and then clearing in xylene.  I then rehydrated them and continued my FISH procedure, I am in the middle of staining, so I won't know if it worked until tomorrow.  I am not even sure if I should continue and add my probe, which is hard to come by.
You might be thinking that there may still be wax on my slides, I thought of that too, but I deparaffinized the same as I always do for IHC, with 3 (3-minute) changes in xylene, 2 (3-minute) changes of 100% and then a change each of 95% and 80% before hydration in water.  I have never had this problem with my IHC staining or anything else, so I am inclined to think that it is the MES buffer that has some type of greasy component to it.
What does everyone think?
 Kim Merriam, MA, HT(ASCP)
Cambridge, MA