That won't be a memory allocation problem, unless the server you're running it on is already all the way at the limits of the swap file. You'd know that, because the server would crash instead of just not getting to a certain step in the SSIS package.

More likely, the step is either taking longer than you expect, possibly because of the dataset size being larger (hence, longer query), or there's something in the package stopping it from getting to that step in the first place, like a malformed process flow (conditions incorrectly set, that kind of thing).

Are you querying data from SQL Server to fill the dataset? If so, running a trace (Profiler or server-side), with begin and end steps logged, will tell you how long the query takes to run. That might be a good place to start.