Just add the following directives in the htaccess file.
# Turn off mod_security filtering.
# The below probably isn't needed,
# but better safe than sorry.
If the above method does not work, try putting the following lines into the
SetEnvIfNoCase Content-Type \
"^multipart/form-data;" "MODSEC_NOPOSTBUFFERING=Do not buffer file uploads"
Another options :
1. Disable the particular line for phpmotion script:
you can change the text "ERROR: Failed to find flength" file in ,cgi-bin/uu_ini_status.pl
make it on : my $flength_file_exists = 1;