Edit field pick list - Cannot save list "Special Characters not Allowed" error message

Edit field pick list - Cannot save list "Special Characters not Allowed" error message

I had a list of entries in a drop down list as follows:

Press: Newspaper A
Press: Newspaper B
Web: Site A
Web: Site B

I wish to add new entries to the list that would appear in the drop down. Since the latest CRM upgrade recently I can neither add new entries or even save the existing entries without the error "Special Characters not Allowed" being displayed. I have removed the : and / characters that I had in some of the entries and was able to save the current list once with out adding new entries. There are no other characters other than A-Z and a-z and spaces in the drop down list entries. What special characters are being referred to and what change took place in the recent upgrade that prompted this error message to start appearing. Finally how do I get round it and continue to add new entries to the list? Is there a maximum to the number of entries in a drop down list?

Thanks
Brixnmorta