Effect of I-Frame on Google Rank

[Kingalan1]

My commercial real estate  web site (www.nyc-officespace-leader.com) allows visitors to search for office space listings. The site sources listings through a third party and they are displayed in an i-frame. The i-frame directs visitors to listing pages such as: http://listings.nyc-officespace-leader.com/getspace.mpl?sp_id=A0173921&cust_id=offspldr

Atleast 10,000 of these pages have backlinks to my site.

My question is the following: Could these tens of thoudands of alpha numeric URLs be detrimental to my sites ranking on Google after the Panda/Penguin updates?

SIte traffic dropped from 7,000 per month to about 3,300 after the April Google update. Rewriting content for dozens of  pages and adding a blog have only somewhat mitigated the negative effects of Panda/Penguin.

Could Google be viewing these links from the third party lisitng provider as a negative when they viewed these links as a plus before?

Any downside to removing the third party links and  parsing these listings from landlord websited and displaying them as part of my site with their own URL, title tag, description tag? Obviously the new URLS would not be alphanumeric.

If these links have not caused the drop in traffic last April, what could be responsible?

Thanks in advance for your opinion!!!

Alan

[kadesmith]

I've seen a few other real estate type sites take a hit similar to what you are describing.  I attribute it to the amount of duplicate content across several real estate sites.  I'd focus on creating unique content/promotions on YOUR site aside from the listings.