Excel stopped working, error 2147417851

Addition: I’ve added in a New WordApplication step and that has worked.:

' DEBUGGING
dim StepMe as String
StepMe = "0"  
System.DebugLog("Step 0")  
Dim word as New WordApplication
StepMe = "z"
System.DebugLog("Step z")
Dim excel As New ExcelApplication
StepMe = "a"  
System.DebugLog("Step a")