1) When importing products via excel, the PortalId is 0. If you manually edit the proper portalid it works fine.
2) Skus (ModelNumers) are formatted as numbers during import. ie: 0001 becomes 1.
This is fixed now in the latest build to be released in the next day or 2. Thanks for your feedback.
PortalId has been added to the product import and version 2.6 is released. I checked out sku and it is handled as a string everywhere in the program and defined as a varchar in the products table you may want to check your xls anytime you open excel with a column that has data like 0001 excel automatically thinks its a number and strips leading zeros, in order to prevent excel from stripping leading zeros from the sku column you have to specifically define the sku column as a "Special" data type under the format menu. Highlight the entire column and right click then choose "Special"