Thanks for the speedy reply:
Here's the log entry for the most recent transaction
WordPress® v3.1.3 :: s2Member® v110606
test.accidentalphotography.com/about/
User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:2.0.1) Gecko/20100101 Firefox/4.0.1
-------- Input vars: ( Wed Jun 15, 2011 5:37:50 pm UTC ) --------
array (
'METHOD' => 'BMCreateButton',
'BUTTONCODE' => 'ENCRYPTED',
'BUTTONTYPE' => 'BUYNOW',
'L_BUTTONVAR0' =>
'business=mail@accidentalphotography.com',
'L_BUTTONVAR1' => 'notify_url=http://test.accidentalphotography.com/?s2member_paypal_notify=1',
'L_BUTTONVAR2' => 'cancel_return=http://test.accidentalphotography.com/',
'L_BUTTONVAR3' => 'return=http://test.accidentalphotography.com/?s2member_paypal_return=1',
'L_BUTTONVAR4' => 'rm=2',
'L_BUTTONVAR5' => 'no_shipping=1',
'L_BUTTONVAR6' => 'no_note=1',
'L_BUTTONVAR7' => 'custom=test.accidentalphotography.com',
'L_BUTTONVAR8' => 'currency_code=USD',
'L_BUTTONVAR9' => 'page_style=paypal',
'L_BUTTONVAR10' => 'charset=utf-8',
'L_BUTTONVAR11' => 'item_name=Description and pricing details here.',
'L_BUTTONVAR12' => 'item_number=sp:70,76:72',
'L_BUTTONVAR13' => 'amount=0.01',
'L_BUTTONVAR14' => 'on0=Referencing Customer ID',
'L_BUTTONVAR15' => 'os0=1',
'L_BUTTONVAR16' => 'on1=Customer IP Address',
'L_BUTTONVAR17' => 'os1=66.185.42.96',
'VERSION' => '71.0',
'USER' => 'mail_api1.accidentalphotography.com',
'PWD' => 'YPJJ7N7U5BEVRNBA',
'SIGNATURE' => 'AFcWxV21C7fd0v3bYYYRCpSSRl31AuA.DWCzlyUV-0YA4W5cjPZb4VYm-BSIKBK5AgZraKa.pF7mVpEnWrAdF2EVNs7b',
)
-------- Output string/vars: ( Wed Jun 15, 2011 5:37:50 pm UTC ) --------
array (
'__error' => 'Error. Please contact Support for assistance.',
)