"...it gives me the error 'Memory spaces do not match.'"

Don't forget that the 8051 architecture has several distinct "Memory Spaces" (or "Address Spaces"); eg, there's CODE, DATA, IDATA, XDATA, etc
Therefore, pointers in an 8051 implementation must contain not only an address but also the Address Space to which that address applies.

I don't know the Tasking tools, so I can't say how they've implemented this, but it sounds like this may be significant for your particular situation.
What does your documentation tell you about this issue?

Does your documentation and/or online Help give you any hints as to possible causes of this particular message?