Commodore 64 with weird "sticky" RAM fault!

This is the oddest fault with a C64 I have seen first-hand. What began as an intermittent failure to power up soon transpired to be caused by reset-protected games, that is games that alter the default reset vector to prevent a soft reset to BASIC (presumably to protect the game code from POKEs or 'cracking' groups). This change would usually be wiped once the C64 has been switched off, but with this particular computer the data in memory persists. A very useful debug program written by user "tfg" on the lemon64 forum shows the extent of the RAM's 'stickiness'. I can power the thing off for several minutes, believe it or not, and the default reset vector has not been reset. Moreover, the program is still in memory. I disconnect all cables from the machine, there is nothing up my sleeve, but it still remembers. Just to reiterate, this program is in RAM!

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