Hi Ruben,
There are few strange things that maybe you can clarify. First, you've asked Amelia for 1 imputation in the second approach, so I'm not sure why there would be more than 1 imputed dataset in the "imputations" list. Next, can you send along your environment (OS type, version, R version, etc, foreach backend) and the error messages you are receiving?
I wonder if this is a problem with the specific dataset. Can you see if Amelia works with the example data?
library(Amelia)
data(africa)
a.out <- amelia(africa, ts = "year", cs = "country", parallel = "multicore", m = 1,ncpus = parallel::detectCores())
If that fails again, I would try to reinstall Amelia either from source or even better from a binary if you are on Mac OS X or Windows.
Hope that helps!
Cheers,
matt.
~~~~~~~~~~~
Matthew Blackwell
Assistant Professor of Political Science
University of Rochester