Hm, that sounds like something caused by Gears, which may cause loss of data or problems like you're seeing.

Can you check to see if you have it installed? The easiest way to do so is to look on the header of the website for either Offline (no Gears) or a green arrow (Gears). You can also look under the Tools menu to see if Gears Settings is listed there or on Google's site for more instructions specific to your OS/browser.

Let me know what you find!

It has happened on systems both with gears and without. It is an intermittent problem. Maybe caused by the update on the system with gears installed? When the non-gears (or gears) system grabs the data, a subset of cases encounters this characteristic, where a postpone function shows it modified to "today", but then when I go to another tab like the main screen the date gets reset back to the earlier date - state is lost. If however I type in a date it is locked in and no such reset to an earlier state happens when going to the main screen. Many of the tasks have no such problem - hit postpone and it locks in on on all screens. But some tasks get in to a state where if you hit postpone the new date's state does not get preserved on other tabs.

Is it gears related? And is an update on a gears enabled system propagated to another machine with no gears installed assured to cause the problem on the non-gears machine?

It sounds like it could be Gears-related. Could you disable Gears to see if it makes a difference?

I recently installed gears on a laptop as well, while using RTM on a desktop and a second laptop. My changes to SmartLists and regular lists from the second laptop, the one without gears, seem to have disappeared.

WHOA! Hey! I logged out of RTM on my desktop and laptop, then uninstalled Gears from the laptop I had installed it on, which has been online all day. When I logged back in all of my missing changes (added lists, removed lists, new SmartLists, etc) suddenly appeared! So much for Gears. It's going to take a while to trust that again...

I use Gears and Fluid on my Mac, since I definitely need offline access to my tasks. I'm also experiencing some strange behavior, mainly with Smart Lists which get parsed wrong (name of task appears as single tags, tag and time not removed from task name).

If I have to disable Gears to get everything in line again, how should I access my tasks when being offline then?

Yes, this is very important for me. ATM I'll just bear malfunctioning Gears because it is better than nothing but this is not a satisfying state ...

so this is possibly a problem by Google Gears, since it is neither compatible with Snow Leopard nor with Safari 4.x

Which is lame ...

But is there a plan for a native cocoa app that would make everything better? i'd approve and pay for it extra ... The current state of affairs is unsatisfying!

... or we just wait until w3c passes this http://www.w3.org/TR/offline-webapps/ and some browser support it ...

okay, i am getting really geared up about this topic (pun intended). Safari is supporting the w3c proposal since 4.0 so it is possible to include offline browsing and the like without Google Gears NOW.

Read the Apple Safari Reference here http://developer.apple.com/safari/library/documentation/iPhone/Conceptual/SafariJSDatabaseGuide/Introduction/Introduction.html