Error when adding first custom breadcrumb: Additional uncaught exception thrown while handling exception.

Hi,

Have used this version of CB for a while, however I've just installed it on a relatively complex installation and it's throwing this SQL error when I try to add my first custom breadcrumb:

Additional uncaught exception thrown while handling exception.

Original

PDOException: SQLSTATE[HY000]: General error: 2006 MySQL server has gone away: SELECT b.* FROM {block} b WHERE (b.theme = :db_condition_placeholder_0) AND (b.status = :db_condition_placeholder_1) ORDER BY b.region ASC, b.weight ASC, b.module ASC; Array ( [:db_condition_placeholder_0] => seven [:db_condition_placeholder_1] => 1 ) in _block_load_blocks() (line 727 of /home/xxxxxxxxxx/public_html/modules/block/block.module).

Additional

PDOException: SQLSTATE[HY000]: General error: 2006 MySQL server has gone away: INSERT INTO {watchdog} (uid, type, message, variables, severity, link, location, referer, hostname, timestamp) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3, :db_insert_placeholder_4, :db_insert_placeholder_5, :db_insert_placeholder_6, :db_insert_placeholder_7, :db_insert_placeholder_8, :db_insert_placeholder_9); Array ( [:db_insert_placeholder_0] => 1 [:db_insert_placeholder_1] => php [:db_insert_placeholder_2] => %type: !message in %function (line %line of %file). [:db_insert_placeholder_3] => a:6:{s:5:"%type";s:12:"PDOException";s:8:"!message";s:334:"SQLSTATE[HY000]: General error: 2006 MySQL server has gone away: SELECT b.* FROM {block} b WHERE (b.theme = :db_condition_placeholder_0) AND (b.status = :db_condition_placeholder_1) ORDER BY b.region ASC, b.weight ASC, b.module ASC; Array ( [:db_condition_placeholder_0] => seven [:db_condition_placeholder_1] => 1 ) ";s:9:"%function";s:20:"_block_load_blocks()";s:5:"%file";s:90:"/home/xxxxxxxxxx/public_html/modules/block/block.module";s:5:"%line";i:727;s:14:"severity_level";i:3;} [:db_insert_placeholder_4] => 3 [:db_insert_placeholder_5] => [:db_insert_placeholder_6] => xxxxxxxxxx/admin/structure/custom_breadcrumbs/add [:db_insert_placeholder_7] => xxxxxxxxxx [:db_insert_placeholder_8] => 94.169.64.201 [:db_insert_placeholder_9] => 1353631214 ) in dblog_watchdog() (line 154 of /home/xxxxxxxxxx/public_html/modules/dblog/dblog.module).

I've flushed the cache in hope, but that hasn't helped. I'm guessing it's a clash with a module, as I know CB works on a fresh install. I can list the modules in use if that would be useful.

Any advice would be appreciated.