The 1M resistor that you removed and added again is basically a hack to
get the memory clock PLL to work. The software fix is supposed to work
in most cases (but as you found there are a few that have problems).
The upshot of having the resistor there is the PLL feedback loop is a little
unstable, so if you try to push MCLK to its highest frequencies (which
at least one version of the X server did, probably based on magic in the
config file) it fails to lock. This makes the video go really odd -- mostly
repeated patterns. If the X server doesn't push the MCLK limits then having
the resistor is good because things are more likely to startup.

Mark