I searched the forums and found this thread:

forum.joomlaworks.net/index.php?topic=9910.0

The same type of thing happens to my site.  A page that was previously CSS styled seems to lose all styling when a SIG Pro gallery is on the page.  Here is what happens.

The website is a pornographic site, so members must log in.  Originally I logged in as an admin and had this problem.  The co-developer also logged in, not as an admin and didn't have the problem.  I made a normal user account to test and didn't have the problem either, but now the problem is back on both Firefox and Safari browsers at all levels of users.  In the meantime I've installed AllVideos Reloaded but the issue wasn't fixed when I uninstalled AVR.  Here are the steps to replicate the problem:

User logs in and navigates to the photos page.  The photos page takes a VERY long time to load and then loads only as a list of thumbnails lined up down the left hand side of the page.  Any text included with the updates is shown.  When the thumbnails are clicked they open in a new window.  None of the page formatting is shown at all.  I'm using a RocketTheme template which is heavily CSS styled, so not even the toolbar shows up!  

I'm using Joomla 1.5.14 with SIGPro 2.0.4  I've tested in both Firefox and Safari.  I can share a link but I must do that over PM, since the links are of an adult nature.

All help is appreciated.  I have no idea what this problem is!

Did you try to use smaller images?
Did you try to change SIG Pro template?
Please pm access to your super admin and of course a link to your site so as to help you..

Hi Katia,

You rock!  Thank you.  I messed around with the gallery templates for a while and nothing happened so I went back to the page to see in which photo updates I needed to resize the photos.  I noticed that five sets were supposed to be on that page but only four displayed!  I unpublished the fifth set and everything was fine.  I went back into the HTML in that set and found a non blocking space.  Deleted the space and published the set again, everything was fine.

Going back through the photo sets I found that SIGPro is just "picky" about your HTML.  If there's anything not web 2.0 about your HTML the page will lose formatting and no galleries after the one with improper HTML will display.

I went back through all 300 updates; four had a non blocking space, one had word cut in half by HTML tag, another three had the gallery plugin enclosed by paragraph tags.  In each case the page took forever to load and instead of just "/photos" displaying in the address bar, "photos?start=55" (with a different number at the end every time) displayed.

Katia, thank you so much for your help, I apologize for wasting your time with such a Noob error!