I found the reason, though there are several reasons for this error from MDX query through SSRS report, what I found is, the functionality of STRTOMEMBER / STRTOSET is getting violated, if the value passed through does not meet the following

1) doesn't match with the datatype of the Tuple

2) the expression was built with error (while designing the expression itself we may miss something)

3) may be some conversion error over the expression value

-x-

in my case the building the expression was the issue.

="[BeginTime].[CALENDARDAY].&["+format(Parameters!FromBeginTimeCALENDARDAY.Value,"yyyyMMdd")+"]"

in the above [CALENDARDAY] should be given like [CALENDAR DAY] so the space between CALENDAR & DAY have given me this headache.

hope this info may help someone.