Here's the limits I found for Excel from the Excel help:
Feature Maximum limit
Open workbooks Limited by available memory and system resources
Worksheet size 65,536 rows by 256 columns
Column width 255 characters
Row height 409 points
Page breaks 1000 horizontal and vertical
Length of cell contents (text) 32,767 characters. Only 1,024 display in a cell; all 32,767 display in the formula bar.
Sheets in a workbook Limited by available memory (default is 3 sheets)
Colors in a workbook 56
Cell styles in a workbook 4,000
Named views (view: A set of display and print settings that you can name and apply to a workbook. You can create more than one view of the same workbook without saving separate copies of the workbook.) in a workbook Limited by available memory
Custom number formats Between 200 and 250, depending on the language version of Excel you have installed.
Names in a workbook Limited by available memory
Windows in a workbook Limited by system resources
Panes in a window 4
Linked sheets Limited by available memory
Scenarios (scenario: A named set of input values that you can substitute in a worksheet model.) Limited by available memory; a summary report shows only the first 251 scenarios
Changing cells in a scenario 32
Adjustable cells in Solver 200
Custom functions Limited by available memory
Zoom range 10 percent to 400 percent
Reports Limited by available memory
Sort references 3 in a single sort; unlimited when using sequential sorts
Undo levels 16
Fields in a data form 32
Custom toolbars in a workbook Limited by available memory
Custom toolbar buttons Limited by available memory
Some important things you might want to note that are probably affecting you:
1. Column width 255 characters
2. Length of cell contents (text) 32,767 characters. Only 1,024 display in a cell; all 32,767 display in the formula bar.
So if you only have one line it will fit only 255 characters. If you have multiple lines Excel 2003 will display up to 1,024 characters. It will hold up to 32,767 characters in each cell though, but only the first 1,024 will be displayed.