Dear Sanjay
I assume you use customer specific classes and not SAP standard ones? If it is a SAP class: you need to check your system. With SAP classes I have nether had similar problems. Is this a problem on test or dev?
May be:
http://help.sap.com/saphelp_40b/helpdata/fr/14/194b6e5733d1118b3f0060b03ca329/content.htm
helps.
As well: http://help.sap.com/printdocu/core/print46c/en/data/pdf/CACL/CACL.pdf
could give some insight
C.B.
PS: I found this thread not related to EH&S but dealing with the same issue: http://scn.sap.com/message/9664396
May be check: https://scn.sap.com/thread/1781964 as well.
PPS: http://wiki.sdn.sap.com/wiki/display/PLM/How+to+create+a+new+class+type
might help as well
And last but not least:
Which contains very useful information regarding classes