Unable to add contacts in MSN Messenger!

Hi,

I am unable to add contacts to my MSN messenger. Following are some details:
1- The contactlist is not more than 60;
2- On my hotmail account, the address-book doesn’t contain more than 100 addresses;
3- Have tried using MSN messengers from different computers & different net connections -all gives the same results.
4- I have deleted a few contacts from my list, still am not allowed to add!

Any ideas what could be the problem?!
Thanks,
Ash.