[Users] No memory left errors and Private Memory Size

Firstly, Happy New Year to all, I am seeing quite a few of these memory errors in the openser log file: *build_contact(): No memory left*. These seem to be occurring when the UA tries to register with Openser. In the last instance I saw, this lasted almost half an hour before clearing up. So I guess what I am trying to find out really is: 1. Is this related to the Private memory size issue I remember reading about a while ago? I am using Openser 1.0.1 and so far have not messed with the default memory size settings from the sources I downloaded. The link on the Openser website about increasing Private memory seems to imply that this could be what is producing these errors. (I refer to this link - http://openser.org/dokuwiki/doku.php/troubleshooting:private-memory-size). 2. Also, if I really have to increase the private memory, I would like to know how to go about it. Since I already have openser installed and the server is already in use, do I have to wipe the server and partitions and re-install the modified Openser or is there an easier way? Can I just recompile the sources and re-install openser over the previous one and get it to overwrite the existing directory (without experiencing any problems with left over files)? 3. How much Private memory is enough to stop these errors? For example, for a system with 1GB of installed RAM should it be using say 768MB? 4. Finally, can anyone tell me the difference between *private memory* and *share memory* in this context? The only difference I am aware of is to do with, for example, shared graphics memory (e.g. for onboard graphics cards on some systems which use up some amount of installed physical RAM memory instead of their own onboard graphics memory). Is this the same thing? Sorry if some of these questions sound a bit basic but I'm coming from a Windows background. Thanks in advance.