[amelia] Error: contrasts can be applied only to factors with 2 or more levels

Hi, I am running Amelia on a cleaned up subset of a single round of the National Longitudnal Survey of Youth data. The subset used in the analysis has 64 variables. I only kept factor variables with 2 to 10 levels in the subset, but when I run the amelia command I get the following error: **** Error in `contrasts<-`(`*tmp*`, value = contr.funs[1 + isOF[nn]]) : contrasts can be applied only to factors with 2 or more levels **** On the other hand the amelia code runs if I specify "incheck = FALSE" in the command options. I am also able to do multiple imputation on this dataset using other R software but am keen to work with Amelia, since I want to utilize the TSCS aspect of multiple imputation that the software provides. Could you shed some light on why I am seeing the error above and also if the imputation with errors suppressed is reliable? Thanks, Nandana Sengupta University of Chicago, Knowledge Lab