Unexpected Behavior from Worksheet to Unembeded Chart

On December 3rd, I described my problem on another message forum dealing with car mpg. Post was never answered and I have added another refueling to the problem.

Preliminary "explanation" before the problem.
I keep track of my gas mileage via a spreadsheet and three corresponding clustered-column charts (Gallons, Trip Miles and MPG).
Nine column-values are the most eye-pleasing.
Problem: I just filled up last week and was going to add the new data.
Column Headings:
DATE, GALLONS, PRICE/GAL, FUEL SALE, ODOMETER, TRIP MILES, MPG
I have formulas to compute FUEL SALE, TRIP MILES, MPG
Rows:
Fill-up dates (total 9 per chart)
(If I'm on the first row of a new worksheet, I label the rows alphabetically B through I; and insert interim numbers to raise the chart columns above the X axis.)
PROBLEM DESCRIPTION
I'm ready to add last week's fillup. Before adding, each chart displays the dates properly (Date #1: 25-Jan through date #8: 25-Oct)
When I replace the interim "I" in cell A-10 with 11/29 (formated to 29-Nov), all three charts end up with two extra dates and are formatted in Mmm-Yy style (Jan-07 through Nov-07). DECEMBER 31ST SEE ADDTIONAL INFO***
I'm thinking I must have a box checked which shouldn't be, or vice versa.

Thanks ever so much,
Stumped

***
Old data sheet still in workbook: 200x Numbers
Chart sheets in workboook:
G 25 JAN 07, T 25 JAN 07, M 25 JAN 07 (Gallons, Trip Miles, MPG)
Action/experiment today, 12/31/07
Add New data sheet: Sheet1
Copy rows 1-9 to new sheet
Manually added input data columns; copied formulas
Disconnected the 3 charts from their sources on 200x Numbers and connected them to the corresponding cells on Sheet1
Added date to cell A10 with the same result as noted above
Copied cells B10:G10 to B11:G11
Tested gallons chart Source: =Sheet1!$A$1:$B$9,Sheet1!$A$11:$B$11
Date labels in chart change from Dd-Mmm to Mmm-Yy with Feb & Jul data disappearing from chart but space still there
Change chart source to: =Sheet1!$A$1:$B$11
On the chart, Columns labeled I and 29-Nov show the same value.
If I delete Row 10:
Date labels change as above.