Why does intellisense "disappear" at times?

I am a rare user of VBA (once a year) for the past 8 years and always have de ja newbie experience. Because I don't recall the DOM very well I rely on intellisense. At times using certain kewords/methods intellisense gives me the impression Im doing something wrong because of its lack of response.

For example I use the Cells method because I am using dynamic single cell references.

Cells(r,c).interior.color =255

Intellisense will die whenever I use the cells method. Why is this?

I've stared using a work around for this intellisense case of A.D.D.

Range(Cells(y, x).Address).Interior.Color = 255

or I type garbage code and clean it up

Cells.Interior.Color=255

This will keep intellisense offering keywords to the DOM challenged. Am I coding in an incorrect fashion to confuse VB?