Mutex error from X5

Since downloading X5 trial, I am seeing large numbers of error reports in my application event log:

Event Type:    Error

Event Source:    Protexis Licensing Service
Event Category:    None
Event ID:    49
Date:        23/02/2010
Time:        17:18:24 (about 20 such entries within a few seconds of this time)
User:        N/A
Computer:    UNICORN
Description:
Failed to Release Mutex
Error ID = Returned Error 288 (or sometimes error 1)

ps -- this is on Windows XP and the same machine also has a full version of X4 in case this is relevant.