I have often had problems changing the number of elements in a cluster in this way. I have often, and reprodicibly had crashes when changing the number of elements in an "Array to cluster" function which is wired up. I always un-wire the function fitst, change the settings and then re-wire.
Maybe this is fixed now, but then again, maybe not.
If you experience a crash, this work-around should do it.
Shane.
Using LV 6.1 and 8.2.1 on W2k (SP4) and WXP (SP2)