On one of my WordPress installs, the "upgrade" link on the plugins page doesn't show for those plugins whose upgrades are available. I just get the "View version X.XX details" link but the automatic upgrade link that is supposed to be there after that is not there. This problem has been there ever since automatic plugin upgrade system was introduced in WP (v2.5 I think).
I've other WP installs on same server (different domains) & 2 other WP installs on the same domain (different sub-domains) which do not have this problem.
Now the only difference that I see in this particular WP install & other installs is that this one (which has this problem) is an old WP install (original was v1.5 when it was released) and then I've been upgrading it (its running latest v2.7.1 right now). The other installs which do not have this problem were installed much after that (with v2.3).
Can anyone please help with determining what's wrong in this particular install & why the automatic plugin upgrade link is not available & what can be the possible solution to this problem?
Its just that upgrading plugins manually one by one is a very time consuming job! :(