Error on my GB

I'm using the verson 2.3.1 and it's been running well. However, I received this error today. What should I do to correct it?? The website is http://www.timmurphyband.com/guestbook/index.php. Thank you!!

Parse error: parse error, unexpected T_LNUMBER, expecting T_VARIABLE or '$' in /home/httpd/vhosts/timmurphyband.com/httpdocs/guestbook/lib/gb.class.php(296) : regexp code on line 1

Fatal error: Failed evaluating code: $100 in /home/httpd/vhosts/timmurphyband.com/httpdocs/guestbook/lib/gb.class.php on line 296

It works again after I deleted two spam entries from the database directly. Thank you!!

All I can think of was there was something in the smiley codes.

For the security purpose, would you suggest me to upgrade the GB to 2.4.2 or Lazarus? Thank you!!

Either or although there has been reports that people are still getting spam with version 2.4.2 of AG.