MDS keeps dropping

[howlingthunder]

Been searching the forums and interweb for a couple of days now and cannot find a solution - hoping someone can help.

BES version 4.1.7.18, MDS using JRE 1.6.0_17 (previously using JRE 1.6.0 rev2)

Every few hours my users can no longer browse the internet and SMIME no longer works. The MDS-CS service does NOT stop running, and event log only has this around the time it happens:

Event Type: Error
Event Source: BlackBerry MDS Connection Service
Event Category: None
Event ID: 15000
Date: 1/28/2010
Time: 8:03:30 AM
User: N/A
Computer: *Removed*
Description:
<2010-01-28 08:03:30.628 PST>:[8518]:<MDS-CS_*Removed*_MDS-CS_1>:<ERROR>:<LAYER = SCM, EVENT = Java heap space>

and:

Event Type: Error
Event Source: BlackBerry MDS Connection Service
Event Category: None
Event ID: 15000
Date: 1/27/2010
Time: 4:29:26 PM
User: N/A
Computer: *Removed*
Description:
<2010-01-27 16:29:26.381 PST>:[2866]:<MDS-CS_*Removed*_MDS-CS_1>:<ERROR>:<LAYER = IPPP, EVENT = Exception, java.lang.OutOfMemoryError: Java heap space
LAYER = IPPP, EVENT = Exception, at java.lang.AbstractStringBuilder.<init>(Unknown Source)
LAYER = IPPP, EVENT = Exception, at java.lang.StringBuffer.<init>(Unknown Source)
LAYER = IPPP, EVENT = Exception, at net.rim.shared.service.log.DefaultMessageLayout.la youtLogMessage(DefaultMessageLayout.java:59)
LAYER = IPPP, EVENT = Exception, at net.rim.shared.service.log.LogTarget.log(LogTarget .java:46)
LAYER = IPPP, EVENT = Exception, at net.rim.shared.service.log.LogServiceImpl.log(LogS erviceImpl.java:466)
LAYER = IPPP, EVENT = Exception, at net.rim.protocol.iplayer.logging.IPLayerLogger.int ernallog(IPLayerLogger.java:52)
LAYER = IPPP, EVENT = Exception, at net.rim.protocol.iplayer.logging.IPLayerLogger.log (IPLayerLogger.java:63)
LAYER = IPPP, EVENT = Exception, at net.rim.protocol.iplayer.thread.ConnectionsInputSt reamesReader.processDeviceInitiatedConnection(Conn ectionsInputStreamesReader.java:274)
LAYER = IPPP, EVENT = Exception, at net.rim.protocol.iplayer.thread.ConnectionsInputSt reamesReader.run(ConnectionsInputStreamesReader.ja va:1117)
<2010-01-27 16:29:26.381 PST>:[2866]:<MDS-CS_*Removed*_MDS-CS_1>:<ERROR>:<java.lang.OutOfMemoryError: Java heap space>
<2010-01-27 16:29:26.381 PST>:[2866]:<MDS-CS_*Removed*_MDS-CS_1>:<ERROR>:<at java.lang.AbstractStringBuilder.<init>(Unknown Source)>
<2010-01-27 16:29:26.381 PST>:[2866]:<MDS-CS_*Removed*_MDS-CS_1>:<ERROR>:<at java.lang.StringBuffer.<init>(Unknown Source)>
<2010-01-27 16:29:26.381 PST>:[2866]:<MDS-CS_*Removed*_MDS-CS_1>:<ERROR>:<at net.rim.shared.service.log.DefaultMessageLayout.la youtLogMessage(DefaultMessageLayout.java:59)>
<2010-01-27 16:29:26.381 PST>:[2866]:<MDS-CS_*Removed*_MDS-CS_1>:<ERROR>:<at net.rim.shared.service.log.LogTarget.log(LogTarget .java:46)>
<2010-01-27 16:29:26.381 PST>:[2866]:<MDS-CS_*Removed*_MDS-CS_1>:<ERROR>:<at net.rim.shared.service.log.LogServiceImpl.log(LogS erviceImpl.java:466)>
<2010-01-27 16:29:26.381 PST>:[2866]:<MDS-CS_*Removed*_MDS-CS_1>:<ERROR>:<at net.rim.protocol.iplayer.logging.IPLayerLogger.int ernallog(IPLayerLogger.java:52)>
<2010-01-27 16:29:26.381 PST>:[2866]:<MDS-CS_*Removed*_MDS-CS_1>:<ERROR>:<at net.rim.protocol.iplayer.logging.IPLayerLogger.log (IPLayerLogger.java:63)>
<2010-01-27 16:29:26.381 PST>:[2866]:<MDS-CS_*Removed*_MDS-CS_1>:<ERROR>:<at net.rim.protocol.iplayer.thread.ConnectionsInputSt reamesReader.processDeviceInitiatedConnection(Conn ectionsInputStreamesReader.java:274)>
<2010-01-27 16:29:26.381 PST>:[2866]:<MDS-CS_*Removed*_MDS-CS_1>:<ERROR>:<at net.rim.protocol.iplayer.thread.ConnectionsInputSt reamesReader.run(ConnectionsInputStreamesReader.ja va:1117)>

Thanks in advance for any advice!