The Magento oscommerce-migration-tool is broken and needs to be manually patched to successfully import. This is the changes I had to do (picked it up from forum posts) to get the import to work. Also, make sure all products have images, and none of your

fix-oscommerce-import-to-magento.diff

diff --git a/app/code/core/Mage/Oscommerce/Block/Adminhtml/Import/Run.php b/app/code/core/Mage/Oscommerce/Block/Adminhtml/Import/Run.php
index 4b5e822..7d46a2a 100644
--- a/app/code/core/Mage/Oscommerce/Block/Adminhtml/Import/Run.php
+++ b/app/code/core/Mage/Oscommerce/Block/Adminhtml/Import/Run.php
@@ -158,7 +158,7 @@ function sendImportData(data) {
 
 
     new Ajax.Request("'.$this->getUrl('*/*/batchRun').'", {
-      method: "post",
+      method: "get",
       parameters: data,
       onSuccess: function(transport) {
         
diff --git a/app/code/core/Mage/Oscommerce/Model/Mysql4/Oscommerce.php b/app/code/core/Mage/Oscommerce/Model/Mysql4/Oscommerce.php
index 4db67d7..026512a 100644
--- a/app/code/core/Mage/Oscommerce/Model/Mysql4/Oscommerce.php
+++ b/app/code/core/Mage/Oscommerce/Model/Mysql4/Oscommerce.php
@@ -696,6 +696,9 @@ class Mage_Oscommerce_Model_Mysql4_Oscommerce extends Mage_Core_Model_Mysql4_Abs
                 }
 
                 if (!file_exists(Mage::getBaseDir('media'). DS . 'import' . $data['image'])) {
+                    $this->_addErrors(Mage::helper('oscommerce')->__('SKU %s cannot find image, looked at: media/import%s',
+                        $data['sku'],
+                        $data['image']));
                     unset($data['image']);
                 } else {
                     $data['thumbnail'] = $data['small_image'] = $data['image'];
@@ -2019,24 +2022,30 @@ class Mage_Oscommerce_Model_Mysql4_Oscommerce extends Mage_Core_Model_Mysql4_Abs
 	 * @param array $notIncludedFields
 	 * @return mixed
 	 */
-	public function convert($data, array $notIncludedFields = array())
-	{
-	    $charset = $this->getDataCharset();
-	    if (!is_null($charset) || $charset != self::DEFAULT_FIELD_CHARSET) {
-    	    if (is_array($data)) {
-    	        foreach($data as $field => $value) {
-    	            if (!in_array($field, $notIncludedFields)) {
-    	                $data[$field] = @iconv($charset, self::DEFAULT_FIELD_CHARSET, $value);
-    	            }
-    	        }
-    	    } else {
-    	        $data = @iconv($charset, self::DEFAULT_MAGENTO_CHARSET, $data);
-    	    }
-	    }
-	    return $data;
-	}
+    public function convert($data, array $notIncludedFields = array())
+    {
+        $charset = $this->getDataCharset();
+        if (!is_null($charset) || $charset != self::DEFAULT_FIELD_CHARSET) {
+            if (is_array($data)) {
+                foreach($data as $field => $value) {
+                    if (!in_array($field, $notIncludedFields)) {
+                        if (@iconv($charset, self::DEFAULT_FIELD_CHARSET, $value) !== FALSE)
+                            $data[$field] = @iconv($charset, self::DEFAULT_FIELD_CHARSET, $value);
+                        else
+                            $data[$field] = $value;
+                    }
+                }
+            } else {
+                if (@iconv($charset, self::DEFAULT_MAGENTO_CHARSET, $data) !== FALSE)
+                    $data = @iconv($charset, self::DEFAULT_MAGENTO_CHARSET, $data);
+                else
+                    $data = $data;
+            }
+        }
+        return $data;
+    }
 
-	/**
+    /**
 	 * Getting saveRows
 	 *
 	 * @return integer