Status
A fix was released for this issue at 6:48 PM AEST on September 16th.
The Issue
When purchasing Guardian Boosts in Guild Wars, players were experiencing a CLIFFY error. This caused the Silver Marks to be removed, but the Boost was not rewarded.
The team, as of 11:10 AM AEST are working on collating player data so any failed Guardian Boosts can be restored to Guild's.Guilds
At the latest, these will be restored before the attack phase of Guild Wars begins.
There is no need to contact Support. Any compensation would be sent out automatically.