My problem I think was that printing to Results in IML in some cases clogs the SAS (even if I quit IML). It may be a problem of printing in general, not IML specific. I had printed a file with one observation and 24 variables and which possibly interfered with previous output.
I will try to play with internal browser/other browser and with the styles in Options-->Preferences and see which one is good.
A temporary solution is to close the Results (internal browser especially) and reopen it when you give a program command.