it seems that this week's update had a new 'feature' we were not told about beforehand. if your collection is over something like 2,500 items, you can not make all tradeable or untradeable with one right-click. the option is there; but it fails to do what it should, informing you in some manner. according to an orc, this change was made to reduce lag on the system. now we can only do the marking manually. or, as the orc suggested, somehow break up things into small enough(under 2,500) chunks.

this may lessen the lag/load on the server, but it puts us at a disadvantage by putting the burden of this action on us to deal with. it is rather time-consuming to do or undo. and it is something that many of us find the need - for whatever reason - to do quite often.

I don't see how 1 operation could cause more lag than 10 operations. If the system was build like it should have been, marking all tradable/untradable should be much easier than setting individual cards or set of cards tradable.
But this is WotC and everything is possible.

Perhaps more importantly, why wasn't this included in the build notes?

I just tried it, the client tells me I have more cards than the OP mentioned, and it just let me mark all tradable and then untradable afterwards....

The limit is 2500 *distinct* objects.  So if you have 2500 different types of land and you have 2 of each of those, you can do them all in one update.