Here is a patch that was on the mailing list for amd64 for 0.6.  I have changed
it to work with the current version.  It works great, have been using since 0.12.

diff -u ipw2200-0.18/ipw2200.c ipw2200-0.18-amd64/ipw2200.c
--- ipw2200-0.18/ipw2200.c      2004-12-14 11:40:41.000000000 -0600
+++ ipw2200-0.18-amd64/ipw2200.c        2004-12-15 22:09:13.401939832 -0600
@@ -210,7 +210,7 @@
 #define ipw_read16(ipw, ofs) __ipw_read16(__FILE__, __LINE__, ipw, ofs)

 #define _ipw_read32(ipw, ofs) readl((void*)(ipw)->hw_base + (ofs))
-static inline u32 __ipw_read32(char *f, u32 l, struct ipw_priv *ipw, u32 ofs) {
+static u32 __ipw_read32(char *f, u32 l, struct ipw_priv *ipw, u32 ofs) {
        IPW_DEBUG_IO("%s %d: read_direct32(0x%08X)\n", f, l, (u32)(ofs));
        return _ipw_read32(ipw, ofs);
 }
@@ -1827,8 +1827,8 @@
        cb->status = control ^src_address ^dest_address;

        /* Copy the Source and Destination addresses */
-       cb->dest_addr = (void *)dest_address;
-       cb->source_addr = (void *)src_address;
+       cb->dest_addr = dest_address;
+       cb->source_addr = src_address;

        /* Copy the Control Word last */
        cb->control = control;
@@ -6817,6 +6817,15 @@
        }

        pci_set_master(pdev);
+#define PCI_DMA_32BIT 0x00000000ffffffffULL
+       err = pci_set_dma_mask(pdev, PCI_DMA_32BIT);
+       if (!err) {
+               pci_set_consistent_dma_mask(pdev, PCI_DMA_32BIT);
+       } else {
+               printk(KERN_WARNING DRV_NAME ": No suitable DMA available.\n");
+               goto out_pci_disable_device;
+       }
+
        pci_set_drvdata(pdev, priv);

        err = pci_request_regions(pdev, DRV_NAME);
diff -u ipw2200-0.18/ipw2200.h ipw2200-0.18-amd64/ipw2200.h
--- ipw2200-0.18/ipw2200.h      2004-12-14 11:40:41.000000000 -0600
+++ ipw2200-0.18-amd64/ipw2200.h        2004-12-15 22:06:17.442689704 -0600
@@ -661,8 +661,8 @@
 struct command_block
 {
        unsigned int control;
-       void *source_addr;
-       void *dest_addr;
+       u32 source_addr;
+       u32 dest_addr;
        unsigned int status;
 } __attribute__ ((packed));