problem of excel.exe process in remote desk

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MS-Excel

Hello,

I'm trying to run excel macro with ruby script in remote desk.

excel = WIN32OLE.new('excel.application')
excel.Visible = true
excel.WindowState = -4137
workbooks = excel.Workbooks
workbook = workbooks.Open(ARGS[0], 2, true)
workbook.application.Run("....")

I had to prepare remote desk to be logged in always for the execution of the excel. because, excel does not support non interactive mode execution.
The above scripts usually working well. but sometime I have a problem that script does not create excel instance correctly. I can find the execl.exe process in the task manager but the interface is not displayed.
Is there someone who had same problem ?

Thanks.