[imp] frame and imp v2.2.0-pre13

[Imp User]

 ( sorry that the version is v2.2.0-pre13 )
 
 Dear all,

 
 I've used imp for 6 months and it's great. Thanks for all the developers
 on this project!!
 
 I have a frame problem and the situation is as follows:
 
 1. I login to imp say http://mail.horde.org/imp 
 2. I can read 4 frames including the main 
 3. Then I browse to other sites say www.yahoo.com
 4. I return to http://mail.horde.org/imp
 5. All the 4 frames can be seen
 6. When I click INBOX on the left bar, problem occurs : 4 frames becomes
 only one frame and all the menu bars disappear.
 
 I've tested it with IE 5.5 and netscape 4.75 and both have problem.
 
 Please help...
 
 thanks and regards,
 Boris