imapd using too much CPU

Hi,

I'm running WHM 10.8.0 cPanel 10.8.1-S114 (on FC2), there seems to be one user who's IMAP processes keep hogging all CPU resources. I ran /scripts/mailperm but no luck ... also checked his mailbox quotas but they were quite within their limits. Also upcp with and without --force didn't help ... neither did upgrading to the release version.

Can someone please tell me what could be causing this problem ? This only seems to be happening with this particular user and i've checked the processes too, they are valid imapd daemons (no cloaked backdoors etc)

Code:

top - 01:47:00 up  3:26,  2 users,  load average: 9.06, 9.55, 9.78
Tasks: 180 total,  15 running, 163 sleeping,   1 stopped,   1 zombie
Cpu(s): 26.8% us, 59.0% sy,  0.0% ni,  2.0% id,  9.4% wa,  0.1% hi,  2.8% si
Mem:   4154736k total,  3474112k used,   680624k free,   238972k buffers
Swap:  4088532k total,        0k used,  4088532k free,  2350888k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
16985 foobar  18   0  2652 1172  852 R 80.7  0.0   9:34.19 imapd
19516 foobar  18   0  2652 1108  816 R 77.2  0.0   5:15.08 imapd
21706 foobar  18   0  2652 1108  816 R 76.6  0.0   1:22.91 imapd

Thanks in advance,
Cyrus

P.S. I know converting to courier could help but sadly this server has > 500 acnts and would crawl to death if I run the conversion..