We've had a few reports of customers being unable to import alphanumeric columns from Excel. One was importing configuration items (serial number and model number) and another was importing a category tree structure (category name) which included both alpha and numeric characters. The configuration items import left a blank space where the serial number and model number should be. The category tree import did not import any category level which had a numeric value in it.
The problem was resolved by high-lighting the columns in Excel and selecting Format - Cells and then picking the Text option on the Number tab.
One of the customers hit a further problem where, even though they did this, they found that the formatting change to the cells did not apply in Excel properly. To get around this, the customer had to select the relevant columns and use the Data - Text to Column feature in Excel. To do this:
Select the range of cells.
Goto the menu Data>Text to Columns
Click Finish
Then they could apply Format - Cells and then pick the Text option successfully. There are some reports online of Excel users having this problem but nothing to indicate what the cause is unfortunately.