mean command with pweight & vce() & over () options

Hello,

I am trying to use mean command with pweight & vce() & over() options, but I get an error message.
"factor variables and time-series operators not allowed"

wgt_all_byphase -> sampling weight variable, continuous
domain2_allage_m -> 1(group1) 2(group1) 9(else)

For some reason I don't know, it works if I delete "pweight(wgt_all_byphase)".

Help!