If you're using eBay4R v0.8 and upgrading to SOAP4R 20061022 or higher broke your setup, here's a patch to fix it (contributed by Mike Smyth): 

diff -Naur ebay4r/lib/RequesterCredentialsHandler.rb /usr/lib/ruby/gems/1.8/gems/ebay-0.8.0/lib/RequesterCredentialsHandler.rb
--- ebay4r/lib/RequesterCredentialsHandler.rb	2005-12-20 18:12:20.000000000 -0800
+++ /usr/lib/ruby/gems/1.8/gems/ebay-0.8.0/lib/RequesterCredentialsHandler.rb	2007-04-13 21:36:04.000000000 -0700
@@ -30,10 +30,10 @@
     HeaderName    = XSD::QName.new('urn:ebay:apis:eBLBaseComponents', 'RequesterCredentials') 
     Credentials   = XSD::QName.new('urn:ebay:apis:eBLBaseComponents', 'Credentials') 
 
-    EbayAuthToken = XSD::QName.new(nil, 'eBayAuthToken')
-    DevId         = XSD::QName.new(nil, 'DevId')
-    AppId         = XSD::QName.new(nil, 'AppId')
-    AuthCert      = XSD::QName.new(nil, 'AuthCert')
+    EbayAuthToken = XSD::QName.new(nil, 'n1:eBayAuthToken')
+    DevId         = XSD::QName.new(nil, 'n1:DevId')
+    AppId         = XSD::QName.new(nil, 'n1:AppId')
+    AuthCert      = XSD::QName.new(nil, 'n1:AuthCert')
 
     def initialize(eBayAuthToken, devId, appId, authCert) 
       super(HeaderName)

Also, Mike has solved the age old problem of http-access2 not working w/ eBay4R. You just need to tell it where to find your SSL certs. Here's an example patch: 

diff -Naur ebay4r/lib/eBayAPI.rb /usr/lib/ruby/gems/1.8/gems/ebay-0.8.0/lib/eBayAPI.rb
--- ebay4r/lib/eBayAPI.rb	2006-10-10 01:04:52.000000000 -0700
+++ /usr/lib/ruby/gems/1.8/gems/ebay-0.8.0/lib/eBayAPI.rb	2007-04-13 22:01:37.000000000 -0700
@@ -134,7 +134,7 @@
 
     # I believe the line below will work after we get the kinks worked out w/ http-access2
     # service.options['protocol.http.ssl_config.verify_mode'] = OpenSSL::SSL::VERIFY_NONE
-    
+    service.options['protocol.http.ssl_config.ca_path'] = "/etc/ssl/certs"
     return service
   end

Change the path to suit your setup.