Attribute forces item price to 0.00 for text fields

[Guest]

I have a heavily modded store and dont know exactly when this bug crept in, but if i have a text attribute field to simply capture some text from the user relevant to the item i.e. their vehicle type it shouldnt affect the price at all as its got no associated fee but what actually happens is that the price is reset to ?0.00 of the item

 

I also notice that if i dont enter any text in the attribute field then price is ok.

 

If i do enter some text then click buy add to cart it shows price as 0.00 but if i then click on the item image to go back to it, the url has been mangled slightly i.e. if i enter test as text

 

http://www.outdoorbits.com/product_info.ph.../68{txt_22}test

 

instead of

 

http://www.outdoorbits.com/product_info.ph.../products_id/68

 

any ideas as to where i should be looking for this bug ???