wordpress 404 errors upon login – no access to dashboard

SFC plugin was being modified to accept avatars in the custom portions of the site. Upon customization, a blank screen appeared. The custom file was restored, however, the blank screen persisted

the log file showed this message:
[error] [client 76.218.207.62] ALERT – configured request variable name length limit exceeded – dropped variable ‘glt_2_JbzUBctP7_YMUY-htPvFIQOjxKcilVdEZ5g_3PRS5s9_3E5ZyFt1z_Z2gd8XNUba’ (attacker ‘76.218.207.62’, file ‘/home/103018/domains/glamstarlife.com/html/index.php’

added php.ini:
[PHP]
; We highly recommend that you leave this options enabled
cgi.fix_pathinfo=1

; Increase maximum post size
upload_max_filesize = 32M
post_max_size = 32M

; Increase execution time
max_execution_time = 300

; pull in EGPCS [Environment, GET, POST, Cookie, Server] variables as globals
;register_globals = true

; For performance reasons, (mt) does not load all of the modules that are available
; into PHP. You may uncomment any one of the following “extension” lines to enable
; the desired module

; Salblotron XSLT
;extension=xslt.so

; save in local tmp
session.save_path=/home/103018/data/tmp

* on a shared server so therefore I cannot make apache or other php changes. I cannot overwrite any defaults in php.ini for web hosting provider.
* disabled plugins then site came up
* reenable plugins then site stayed up
* now I can register through regular wp system (not Simple Facebook Connect)
* login takes me to a 404 error and unable to access anything but the headway editor.
* tried replacing theme to access admin section – did not work
* user can comment and view posts but cannot post.
* that’s where things stand.
* areas of possibility – .htaccess, database corruption (did not see any corruption in user tables), and permalinks not set right in .htaccess

Can anyone assist me in solving this issue?