The EQ issue is a known issue, stemming from the fact that Rockbox is not sufficiently optimized to do the signal processing necessary for the EQ in real time.
There is also a known issue with the 4g related to frequency scaling. There is a workaround for this, which increases stability by disabling frequency scaling. If you look in the "unsupported builds" forum, there is a build by "Mikeage" which incorporates this workaround. I've seen a number of reports from 4g owners that this build increases Rockbox's stability. Take a look for that build and try it.
For more information, search for "frequency scaling bug" or similar terms.