Can you find out what proxy your university is using? I've read in the forums that EZProxy is currently the only proxy system that Zotero supports right now, though my (UK) university uses Squid for both on and off-campus access, and it works fine for me.

I'm not sure the easiest way to determine this, short of asking your University IT department, but it seems I've seen the name of the proxy on error pages returned by the proxy itself on occasion. Do try to find out the name and post it (perhaps with the name of your university as well). I'm not sure how solvable this problem is, but if there are solutions, they will probably come from trying to work with specific proxy software directly.

Thank's a lot for your comments. Good to know that this is a known issue. More general support for these sorts of proxies would indeed be a good thing.

I'm experiencing this problem (of not having the buttons appear in the url address bar), but only on some database and journals, even though all of them are routed through my school's internal proxy.

For some databases (Jstore, Project Muse, Wilson Plus), the icon does not appear in my address bar
http://0-www.jstor.org.ariadne.kzoo.edu/view/00218537/ap010102/01a00060/0?currentResult=00218537+ap010102+01a00060+0,00&searchUrl=http://www.jstor.org/search/AdvancedResults?hp=25&si=1&q0=david+robinson&f0=au&c0=AND&wc=on&sd=&ed=&la=
http://0-firstsearch.oclc.org.ariadne.kzoo.edu/WebZ/FSFETCH?fetchtype=fullrecord:sessionid=fsapp9-40098-f8zxyuc5-ytuoel:entitypagenum=6:0:recno=10:resultset=2:format=FI:next=html/record.html:bad=error/badfetch.html:entitytoprecno=10:entitycurrecno=10:numrecs=1


However, with others, e.g. Proquest, I have no problems and the icon appears.
http://0-proquest.umi.com.ariadne.kzoo.edu/pqdweb?index=6&did=448222591&SrchMode=3&sid=1&Fmt=3&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1195048376&clientId=41099&aid=1