Thanks Andrew,
1. I started working here mid last Dec. the previous person of the position told me that running period end/month end in A/R, A/P is optional, so we don't usually do it. As I remember that I did only once 'month end' for Dec. and didn't run month end before running year end. However, I did the same way in A/P,, but everything in A/P is fine.
2. Our Year end is April 30; Not sure what happened in last Oct. (October service pack??), we may had our software updated in last Oct.
3. I can still find those transactions(Invoices & Credits) during that peiod in Adagio OrderEntry. However, as the customers payments history exist in A/R only.... I lost the history how the customers paid those invoices and/or A/R ajustment ..related data in A/R!