I have seen this posted before!
As far as I can tell 7.04 and 7.10 are no longer supported. Online upgrades will not work. An alternative would be an upgrade to a newer version, such as 8.04 (Long Term Release) or on up to 9.04. Several months ago I experianced much the same on an older laptop with Dapper Drake and went ahead and installed 9.04 after a data backup. I could be wrong but it might be your best option.
I like the newer version because of all the new features.