@safakoner:
are you sure ? or have you simply forgotten to create a new scene before unloading/reloading your plugins ?
( maya cannot “uninitialize” plugins ( propper deregistration/unloading ) , which are still in use - or if there are still any of these nodes in the active scene … so the plugins get not properly unloaded ( force ) , and therefore , once reloaded - there is still the same (old version ) of the plugin active )
i just wrote 2 plugins , some days ago in maya2011 - and while working on them , added more attributes to them - and reloaded them all the time , while creating them . and did not have this problem .
i remember i had the same problem ( restarting maya all the time ) 2 yrs ago , until i found out - either to create a new empty scene , before unloading/reloading the pluging , or
delete ‘ls -type “myCustomNode”’;
these nodes, before in unload/reload
but maybe i misunderstood you - and you meant something else . ( winxp64 / maya2011 hotfix1 )