computationally singular error with mice()

imp<-mice(mydataframe, seed=1)

When trying the above command, I got the error term:

 iter imp variable
  1   1  medu
Error in solve.default(xtx + diag(pen)) : 
  system is computationally singular: reciprocal condition number =
1.16487e-025/

What does that mean? How can I address this issue? My dataframe has 257
observations for 99 variables. Could this be the origin of the problem?
Could anyone helps me out? Thank you!

Fei

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