After upgrading to 2.7.10 in Joomla 1.5 there are no pay option listed in the Pay Options section. New pay options can be entered and they are selectable from the drop down on the Discounts & Fees tab in the Events section.
2.7.10 did not change anything regarding pay options. Haven't had any other reports like this so I have no idea what the issue could be. Whatever it is, is probably some fluke issue on your site. Are you saying your old pay options aren't there anymore? Wouldn't make sense. If you can't sort things out, submit a ticket with full details of the issue.