Apache 2.4.10 AH00485: scoreboard is full, not at MaxRequestWorkers (Apache Users)

Problem: Apache server will stay up for random amount of time, usually days, but eventually enters a hung state. When hung the CPU load gradually spikes on the machine
and new web server requests are unresponsive.

Error logs typically contain lots of these:

Wed Jan 28 16:06:58.667188 2015] [mpm_event:error] [pid 25336:tid 1] AH00485: scoreboard is full, not at MaxRequestWorkers

I have done a lot of web research on this top and have found many cases where others o=have had the same/similar issue but no real solutions. Seem very close to this bug report: https://issues.apache.org/bugzilla/show_bug.cgi?id=53555

Environment:

LDOM (VM) SunOS myhostname 5.10 Generic_118833-36 sun4v sparc SUNW,Sun-Fire-T200

8G RAM

http Conf:

StartServers                8
MinSpareServers             Not set
MaxSpareServers             Not set
ServerLimit                 256
MaxRequestWorkers           100
MaxConnectionsPerChild      1000
KeepAlive                   On
TimeOut                     3000
MaxKeepAliveRequests        50
KeepAliveTimeout            2

Current non-hung Score Board:

Server Version: Apache/2.4.10 (Unix)
Server MPM: event
Server Built: Oct 30 2014 16:29:03

Current Time: Wednesday, 28-Jan-2015 10:59:39 PST
Restart Time: Wednesday, 28-Jan-2015 09:49:21 PST
Parent Server Config. Generation: 1
Parent Server MPM Generation: 0
Server uptime: 1 hour 10 minutes 17 seconds
Server load: 0.60 0.46 0.41
Total accesses: 1134 - Total Traffic: 2.2 GB
CPU Usage: u9.07 s16.94 cu609.51 cs69.31 - 16.7% CPU load
.269 requests/sec - 0.5 MB/second - 2.0 MB/request
1 requests currently being processed, 99 idle workers

PID Connections     Threads Async connections
total   accepting   busy    idle    writing keep-alive closing
25337   0   yes 1   24 0   0   0
25338   1   yes 0   25 1   0   0
25339   1   yes 0   25 0   0   1
25340   1   yes 0   25 0   0   1
Sum 3       1   99 1   0   2

Any thoughts/comments on http conf tuning, OS patches, apache bug fixes appreciated.

This is a production server, so you can imagine, having it go down at random times (usually when I am asleep) is not fun!

Thanks.
MJ