Access 2003 forms VERY SLOW when opened in prior versions

I have an interesting phenomenon that is occurring.

I have Access 2003 installed on my machine, and most of my clients are using Access 2000 or Access 2002. If I take an existing database that was created in a version of Access prior to 2003, and either update forms/reports or create new forms/reports in 2003, when I attempt to open them again in the prior version of Access (i.e. on my client's machine/server) their performance is severely compromised. They run extremely slowly, particularly to open the form. The same form/report when run in 2003 works quite quickly, and if I re-design it in the prior version of Access, it runs OK on the old version, too.

I am using quite a bit of code under my forms.

I have searched the Microsoft website, and was unable to find any documentation on why this was occurring, and was wondering if anyone had any input on what the problem was? or if anyone else has experienced this, and had a solution as to how to fix it. This is a bit challenging, as all of the things I design are ultimately NOT going to be used on my machine, but I LOVE the new design features in 2003.

Thanks.
Vee

PS: Please try to refrain from blatant Microsoft bashing -- I know, it's difficult --, as this is what I  use, and know, and I really like it.
Thanks.