C64 and Murphy's Law

Well Murphy's Law has struck.
After selling my SX64 my C64 breadbin decided it's time to go on strike.
It's showing 30719 bytes free rather than the 38911. Although I get a cursor and can load stuff using the turbo chameleon it fails to run anything.
Discovered this when I decided to test my MMC Replay as it is no longer required (replaced with a version that works on the Vic20, 64, 16 and Plus4).
Any ideas what's wrong? I'm thinking maybe a ram chip failure?
After selling my SX64 my C64 breadbin decided it's time to go on strike.
It's showing 30719 bytes free rather than the 38911. Although I get a cursor and can load stuff using the turbo chameleon it fails to run anything.
Discovered this when I decided to test my MMC Replay as it is no longer required (replaced with a version that works on the Vic20, 64, 16 and Plus4).
Any ideas what's wrong? I'm thinking maybe a ram chip failure?