Weird memory card problem

Bought a 2nd hand PS2 yesterday, and before going all the way back to kick the seller's ass ("yes sir it works perfectly") I'm trying to fix it. This is the problem:

When trying to load or save games, the PS2 says "memory card not inserted". The strange thing is that when accessing the cards through the browser, I can get on them and even delete the old savegames.

It happens with both original PS2 games that came with the console (Gift and Resident Evil X). Tried all combinations on both slots with two different working cards (both original PS2), but the message stays the same.

The memory card that came with the console had savegames of the game Gift on it, so it has worked before.

So, message is "Memory card not inserted" but through the browser I can see both cards in both slots and even modify them (delete savegames). I've been breaking my head over this one, hope someone can help...

i have the same problem with some cards they not recognised on my slim or fat or ps3.
you can try this.
buy 64mb memory insert into one slot try transfer saves to it from the other card in other slot..try putting cards in diff slots sometimes it works....
now also some people have zipped saves they have to be
un-zipped first but you need the cheat disc that zipped them to reverse the zip..
try cleaning the insides of the ps2 memory slot and card also there might be dust blocking contacts...

yes i get that it says same thing..im not quite sure whats going on at all,but at a guess the cards are not quality products etc and faulty...sometimes a gentle movement will get the ps2 to see the saves...this is an old problem and no-one can give a direct answer for a fix im afraid....
where you from !! im in england

oh right so your pal system like me..
i myself think its the copper connections and that the cards are not sponsered make from sony..
best to buy a 64mb sony make..theres plenty of cheats available..what game was it when this all started!