Random 30s hangs with YouTrack 4.1.1

I'm having random 30s hangs after upgrade to 4.1.1 from 3.x on my YouTrack server w/ dual core processor & 16GB RAM. Below is the statistics screen. I guess there is something wrong with my server configuration after 4.x upgrade:

Available processors    4
Available memory    455.1 MB
Allocated memory    436.4 MB
Used memory    402.9 MB
Uptime     10 hours, 53 minutes, 33 seconds and 936 milliseconds (started at den 13 december 2012 kl 0:47 +01:00 )
Online users     Users: 14 (max is 15 , 19 minutes ago (11:22) )
Sessions: 15
Windows: 28
Database size (without blobs)    1.5 GB
Text index size    30.2 MB
Database background threads    2
Pending asynchronous jobs    0
Number of cached results in the database queries cache    455
Database queries cache hit rate    80.85%
Blob strings cache hit rate    67.21%
Total transactions    1235
Transactions per second    0.03
Requests per second    0.58
Notification Analyzer Queue Size    0
Notification Sender Queue Size    1
User Action Job Processor Queue Size     0
There is no executing job.