I believe the subject id's are currently limited to around 32000 due to a bug that will be fixed in an upcoming version. See:
http://www.empirisoft.com/support/showthread.php?t=239
This can lead to overwriting if:
1. the overwrite warning is turned off or bypassed
2. both subject IDs are over 32000 because both will be treated as subject 0
3. or subject IDs contain letters as alpha-numeric codes are not treated as valid
Data for a subject ID if 24025 should save fine. There is no reason I can think of as to why data from a subject ID of 44036 would overwrite it because that data would be recorded as if the ID were 0. However, as above, overwriting could happen only if the first ID had actually been over 32000 or if the IDs contained letters (again because they would be treated as subject ID = 0).