First of all, thank you guys for the answers. I´ve been busy with this same work, that is why i haven´t checked your replies to this post before. Sorry I didn't come earlier.
With respect to Cap'n Refsmmat question, I guess not. The routine I wrote goes step by step because, in every step, it generates the data that the next step will require. That is why I can't make use of parallelization I suppose. But I still don't see why can't Matlab use more memory. Ain't the next statement true?: "more memory I get, faster the calculation proccess will be".
Answer to ecoli: I'm not sure. I was studing that idea when for other reasons i have to make some changes to part of the algorithm. Remember what I say before about the routine: "it cannot be simpler than already is". Well, to my surprise, yes it can. Reading the Matlab help files, I found out that there were some functions that came along with the program which does most of the work I wrote by my own. So for the sake of simplicity, I replace the vast majority of the routine by a few lines. There's always room for improvement.
To khaled: I've tried n°1, doesn't seem to make a difference. With respect to n°2, I'm on my way to studying it along with StackOverflow thing. Thank you for the info.
After I simplify the code, it starts coming to a solution really fast. My guess is that the previous routine uses so many variables that were define at the moment of being use that it slows the whole chain of calculations. Most likely, the implicitly define functions that come with the Matlab code make a better use of the memory assignation to the program variables.
Thanks again for the comments and the information.