Commas in a vector not accepted

I seek for advice as to how to overcome a following bug. R3.1.1 (windows) has trouble with accepting commas when I try to enter a vector "vector<-(1,2,3,4,5)". In fact, it does not accept any delimiter, giving an error message like this: unexpected ',' in "vector<-(1,". The trouble appeared a few months after installation. Reinstallation of the program does not fix the problem. Please help! Thank you!