If you wanted to get to the bottom of it, you could try attaching a debugger (e.g. gdb) to the R process, and trying to get a backtrace to see what's crashing when os is loaded. For example:
First, close any running instances of RStudio, and then launch a new lone RStudio instance.
Then, in a terminal, start GDB and have it attach to RStudio. You should be able to do this with:
sudo gdb -p `pidof rsession`
If you do not have the pidof utility installed, you can run Sys.getpid() in your R session to get the session's process ID.
After this, GDB should (hopefully) successfully attach to the process. Next, we'll instruct GDB to log to a file:
set logging file rstudio.log
set logging on
Finally, we'll tell GDB to let RStudio continue running:
continue
Now, return to your RStudio session and try running the code that triggered the crash. With luck, if RStudio crashes, GDB should catch the fault. Return to GDB, and enter:
backtrace
You should now be able to quit GDB with
quit
and then make the file at 'rstudio.log' available to us for further inspection.