Phone... I think the apps2sd WITHOUT rooting is not capable on the NON-ROOTED official version of Android which Sprint has on the Hero. Lol... I'm not positive, but pretty sure this is the case.
Anyway, search always first, there's tons of information here that'll answer your questions. The limits will come prior to exceeding available memory just due to too many apps being loaded on the phone. Also, working with the Application Manager in Settings will go far to releasing used memory and contrary to belief this will not be cleared when SOFT booting the phone. You have to go in there and clear out memory/cache. Be extremely careful if you try to clear "DATA" as it will wipe information from apps or render them useless. I am rooted so have the luxury of using an app like cachemate which automates the process. Otherwise I would suggest clearing the browser cache, photo's, and mail to name a few. Those will eat up some memory in the form of cache pretty fast. Also, go into setting in the browser and lower the cache size.
I don't know if this will clear your error, but thought it might help.
Regards,