st: Imputing error: Obs. nos. out of range

["Ploutz-Snyder, Robert (JSC-SK)[USRA]" <robert.ploutz-snyder-1@nasa.gov>]

I'm trying to run ice imputation on a dataset and running into an error that I need some help with. I can successfully run a "dry run" ice command, but when trying to run even 1 imputation I get the error.  

Here's my command:
ice x1 x2 x1x2 x4 z_x5 x6 x7 x8 x7x8 x10 x11 x12 x13 z_x14 y1-y6 z_y7 z_y8 y9-y22, m(1)   passive(x7x8:x7*x8) saving(mrid_imputed, replace) seed(112233)

and here's the error that I get:

Imputing Obs. nos. out of range
r(198);


Advice??

p.s. fyi.. there are a lot of vars here but not all have missing values to be imputed--included to inform the imputations of the others.  Also, x7x8 is an interaction term that is passive, as specified.  Similarly x1x2 is also an interaction term from x1*x2, however x1, x2 and x1x2 have no missing values so x1x2 does not need to be specified as passive.  In fact, if it is specified as passive, ice returns an error " passive definition x1x2 = (x1*x2) redundant: x1 x2 has no missing data.
1 error(s) found in option passive(x1x2: x1*x2\x7x8:x7*x8)"   


Robert J. Ploutz-Snyder, PhD 

*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/