2nd EDIT:
I decided to abandon this project. Basically can't get Oclvanitygen to work in Windows with sequential search and the speeds seem very slow when using a 1x riser. It would take too long to find the 51st key and 52nd and 53rd would take months.
I had a look at the vanitygen code the last couple of day's to see how to make the sequential search.
I just needed a minor change to have the CPU code to run from EC_key=0x01.
Using the online generator at gobittest(dot)appspot(dot)com/VanityAll a key can be made to generate an offset or start code. (for the -P split-key function)
There are still two issue that need to be solved
1) when starting from 1, there are parts of the code that perform an EC_POINT_ADD on two equal value's, here a EC_POINT_DOUBLE is needed.
2) when running multiple threads the old code uses a random key generation to make sure the threads used unique values, currently all my threads run the same data.
1) Is no issue when an offset key is used
2) I just execute the code in single thread, and run the executable #cpu times with another offset start code.
Since I don't have a GPU system I don't know if the change in that code there is just as hard/easy.
I was kind of curious what code changes you made to get it to run.