When I login, execute queries, etc using the web services, I'm randomly getting HTTP 500 errors, when the error occurs on login, I get the following fault:

<LoginFault xmlns="urn:enterprise.soap.sforce.com">
<part name="code">
<code>UNKNOWN_EXCEPTION</code>
</part>
<part name="summary">
<summary>when invoking endpointAddress 'https://www.salesforce.com/services/Soap/c/6.0', UNKNOWN_EXCEPTION: java.lang.OutOfMemoryError</summary>
</part>
<part name="detail">
<detail>AxisFault faultCode: {urn:fault.enterprise.soap.sforce.com}UNKNOWN_EXCEPTION faultSubcode: faultString: UNKNOWN_EXCEPTION: java.lang.OutOfMemoryError faultActor: faultNode: faultDetail: {urn:fault.enterprise.soap.sforce.com}fault: <exceptionCode>UNKNOWN_EXCEPTION</exceptionCode> <exceptionMessage>java.lang.OutOfMemoryError</exceptionMessage></detail>
</part>
<part name="payload">
<LoginFault xmlns="urn:fault.enterprise.soap.sforce.com">
<exceptionCode />
<exceptionMessage />
<exceptionCode />
<exceptionMessage />
</LoginFault>
</part>
</LoginFault>