[imp] Anyone else getting long delays after login, then things work fine until new imap connections opened? (cyrus imap 2.3.x)

[Darrell Budic]

Strange problem I havn't been able to track down here: After logging  
in to Horde, the web browser clears the screen, then things pause for  
30 seconds to a few minutes, and then my sidebar and horde portal  
page come up normally, and IMP runs fine for a while. If you stay  
logged in long enough for your imap sessions to time out, there can  
be another long pause, then things run normally for a while. Very  
odd, very annoying. This install was working fine for a while, not  
sure which update screwed me up, and I havn't been able to roll back  
and resolve it.

Specific questions:

Anyone seen this and fixed it? How?
Anyone using cyrus imap 2.3.x and working correctly?

Versions:

Apache: 1.3.37 (slackware 11 package)
php: 4.4.7 (slack 11 package, seems to have c-client 2004g)
also tried
php: 5.2.3 (own compile against c-client 2006f) (with mcrypt)
imap: cyrus 2.3.x (tried 2.3.1 -> 2.3.8, currently 2.3.8)
horde: 3.1.4
Imp: H3 4.1.4
Ingo: H3 1.1.3
Jeta: H3 1.0
Mimp: H3 1.0.1
Passwd: H3 3.0.1
Turba: H3 2.1.4

Important config info:

Using a composite auth driver to flip between Imp and MIMP auth, from  
the wiki. Tried switching back to pure IMP, no change.

Specific things I've tried:

Various versions of cyrus imap, no change.
Monitoring IMAP connections to server, it looks like it auths fine,  
and quickly pulls info from the imap server, then hangs somewhere in  
php processing before returning.
No errors are logged by apache, imap, or php. Turning debugging on in  
horde also produces no relevant errors. Turning full debugging on in  
php produces no relevant errors.
Horde logs the login immediately after the page is submitted, then  
things pause before displaying the portal page.
I've tried c-client version from 2004g -> 2006f in php 5.2.3, no  
change in effects.
Cleaned up a bunch of old preference data and optimized my mysql  
tables, ensured they were all up to date.
Test imap logins (from imp/test.php) return immediately.
Installed eaccellerator on php 4.4.7, no changes.
Been through the FAQ, searched the mailing list & web, and the wiki,  
can't find reports of anything quite like this.
Checked my configs, as far as I can tell, they are correct for my  
setup. Nothing useful in the performance tuning doc, either.
The server is not loaded, and has lots of free ram.
Tore out some hair, no help there, alas.

Any ideas or comments appreciated, I'm running out of ideas for this  
one... Knowing if anyone was successfully running a similar config  
would be useful to me, I'm preparing a new bit of hardware to test  
with too.

Thanks!

   -Darrell