I'm thinking it was probably just one of the connector pins not connecting right. Taking apart the memcard and putting it back together might have adjusted the connector pins so they all connect. Also, might wanna try using the head of a pencil eraser on the connector pins of the memcard. That should take off any residue or dirt on them.
Model: NTSC SCPH-39001/R (think it's a v7)
Mod: PS1 Exploit Softmod
Harddrive: Internal 40GB Seagate ST340810A
External drive: Apple iPod (in Disk Mode)